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### Course: 6th grade>Unit 6

Lesson 8: Writing algebraic expressions introduction

# Writing algebraic subtraction expressions

In this lesson, we learned how to turn word statements into algebraic expressions. We practiced with examples like "two less than x" and "y fewer than three." Understanding how to translate words into math helps us solve real-life problems and makes algebra more fun! Created by Sal Khan.

## Want to join the conversation?

• this place is amazing. Thank you Khan Academy
• this is very simple. maybe that why no one has commented?
• everyone has tho
• When we swap why can't we have it the other way like when we have x-2 why can't it be 2-x i know it is incorrect already but it is still a question?
• If you have 7 apples for sale and I buy 4, you still have three apples. That's 7-4= 3. If you have 4 apples for sale and I buy 7, not only do you have no more apples, but you still owe me 3 apples because I gave you the money for 7, and you only gave me 4. That's 4-7 = -3. They're all the same numbers, but in different orders, giving us vastly different results.
• Instead of x-2 why can't we do 2-x?
• 2-x is incorrect.
Why, yes because X is variable. So X can be sometime 2,6,1 or whatever.
So example:
If 2-x x=5
then 2-5 = -3
so this is wrong answer
sorry, I'm not that good at English.
• Hey, question here. What if I said x subtracted by y. That would be x - y, simple! (Right? Idk.) SO, what if I said x subtracted from y. What would that be? Thanks!
• x subtracted from y would be y - x.

Have a blessed, wonderful day!
• I have no questions
• p-a is this right
• what is triply m
(1 vote)
• how do you add it
(1 vote)
• this messges is from 20202 dont four get me

## Video transcript

- [Instructor] We have different statements here that can each be expressed as an algebraic expression, and as you might have guessed, I would love you to pause this video and try to write each of these statements as an algebraic expression before we do it together. All right, now let's work on it together. So this first statement, we have two less than x. So my brain thinks, all right, let me start with x, and how am I going to get two less than that? Well, I'm going to subtract two. And this is an interesting example because you see the order that we see it in the sentence is not the order that we would necessarily write it in the expression right over here. Very important to think about, what is going on here? What is being described? Now, this next statement, y fewer than three. Well, in my mind, I'm going to start with three and I'm going to be y fewer than that. So I'm gonna start with three and then I'm going to be y fewer than that. Now, these first two statements are similar in that you have something less than something else or something fewer than something else. They just swapped the number and the variable. Now, this third statement, x decreased by five. So my mind is thinking, what am I starting with? I'm starting with an x and I'm decreasing it by five. So I can do that as minus five, or I'm gonna take five away from it.