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Evaluating expressions review

An algebraic expression like 3x can be evaluated for any value of x. Say x=4, then 3x = 3*4 = 12. In this article, we review how to evaluate algebraic expressions.

What does it mean to evaluate an algebraic expression?

An algebraic expression like 2, x, plus, 3 can be evaluated by substituting a value for x. For example, if x, equals, start color #11accd, 4, end color #11accd then:
2x+3=24+3=8+3=11\begin{aligned} &2x+3 \\\\ =& 2\cdot \blueD{4}+3 \\\\ =& 8+3 \\\\ =& 11 \end{aligned}
We can also evaluate more complicated expressions that have more than one variable. For example, we can evaluate 10, plus, 2, p, minus, 3, r when p, equals, start color #11accd, 4, end color #11accd and r, equals, start color #e07d10, 5, end color #e07d10:
10+2p3r=10+2435=10+815=3\begin{aligned} &10 + 2p - 3r \\\\ =& 10 + 2\cdot\blueD 4 - 3 \cdot \goldD5 \\\\ =& 10 + 8 - 15 \\\\ =& 3 \end{aligned}
Want to learn more about evaluating expressions? Check out this video. And here's a word problem video if you're curious how this concept might apply to the real world.

Practice

Problem 1
Evaluate the expression 7, plus, 4, b when b, equals, 3.
  • Your answer should be
  • an integer, like 6
  • a simplified proper fraction, like 3, slash, 5
  • a simplified improper fraction, like 7, slash, 4
  • a mixed number, like 1, space, 3, slash, 4
  • an exact decimal, like 0, point, 75
  • a multiple of pi, like 12, space, start text, p, i, end text or 2, slash, 3, space, start text, p, i, end text

Want more practice like this? Check out this basic exercise and this more advanced exercise.

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