Main content
Algebra (all content)
Unit 1: Lesson 5
Writing algebraic expressions introduction- Writing basic expressions with variables
- Writing basic expressions with variables
- Writing basic expressions with variables
- Writing expressions with variables
- Writing expressions with variables
- Writing expressions with variables & parentheses
- Writing expressions
© 2023 Khan AcademyTerms of usePrivacy PolicyCookie Notice
Writing expressions
Learn to write algebraic expressions in and out of word problems.
Why do we have math if we can describe things in words?
Sometimes in math we describe an expression with a phrase. For example, the phrase
"2 more than 5"
can be written as the expression
2, plus, 5.
Similarly, when we describe an expression in words that includes a variable, we're describing an algebraic expression (an expression with a variable).
For example,
"3 more than x"
can be written as the algebraic expression
x, plus, 3.
But why? Why use math if we can describe things in words? One of the many reasons is that math is more precise and easier to work with than words are. This is a question you should keep thinking about as we dig deeper into algebra.
Different words for addition, subtraction, multiplication, and division
Here is a table that summarizes common words for each operation:
| Operation | Words | Example algebraic expression |
|---|---|---|
| Addition | plus, sum, more than, increased by | x, plus, 3 |
| Subtraction | subtracted, minus, difference, less than, decreased by | p, minus, 6 |
| Multiplication | times, product | 8, k |
| Division | divided, quotient | a, divided by, 9 |
For example, the word "product" tells us to use multiplication. So, the phrase
"the product of 8 and k"
can be written as
8, k.
Let's take a look at a trickier example
Write an expression for "m decreased by 7".
Notice that the phrase "decreased by" tells us to use subtraction.
So the expression is m, minus, 7.
Let's try some practice problems!
Basic expressions
More complicated expressions
Word problems
Want to join the conversation?
Why do you talk in this ducument that 3 more than x is x+3? It should be3+x(2 votes)
Because of the commutative property of addition "x+3" and "3+x" mean exactly the same thing. Both are acceptable translations of the phrase.(2 votes)
I have a problem with sentence problem like this:Write an expression for "
8
less than the product of
7
and
x
". and I wrote 8-7x but they gave me wrong how I can answer that ?(2 votes)
because it says "8 less than", that means that 8 is supposed to be subtracted from whatever part of the expression is after it, so the answer would be 7x-8. i hope this helped. :)(2 votes)
How do I solve this problem 8 squared(2 votes)
I have a weird problem, when I practiced on khan on subtraction with algebra it showed something like this p - 6 I use that example to do my subtraction problem on IXL but it said it was wrong I had to put the number then the letter.(1 vote)- "p - 6" and "-6 + p" are equivalent and it shouldn't matter which term comes first. The commutative property of addition tells use the 2 expressions are identical. However, you may have been given some explicit directions in IXL that asked you to write the terms in a certain order. If you didn't follow their instructions, that could have caused it to be wrong.
The other possibility is that you confused "p - 6" with "-6p". The first one is subtraction. The second one is multiplication. These are different.
Hope this helps.(2 votes)
These were some pretty easy questions. The problem is that its very confusing for which order I should put the problem in.(1 vote)
why are theas from like 4or5 years ago(1 vote)- The site defaults to show you to top rated questions and answers. These are generally older because it takes time for votes to accumulate. They also might be very relevant to what you are looking for. If you want to see the more recent questions & answers, change the sort sequence to "recent".(1 vote)
- If you need help, you need to post more information that just saying "im stuck".(1 vote)
What is this? Is this in High School. I've got 3 years till High School(1 vote)- But this is just the easy part of algebra 1(1 vote)
- This stuff is pretty easy but i can never be too sure. That is why i'm going back to the basics of it to learn it again and improve my skills(1 vote)