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Algebra 1

Course: Algebra 1 > Unit 1

Lesson 3: Substitution and evaluating expressions
Math
Algebra 1
Algebra foundations
Substitution and evaluating expressions
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Evaluating expressions with two variables: fractions & decimals

Google Classroom
We've already evaluated expressions with two variables. Now it's time to do it with fractions and decimals.
Khan Academy video wrapper
Evaluating expressions with two variables: fractions & decimalsSee video transcript

Let's study another example.

Evaluate start fraction, 1, divided by, 3, end fraction, a, minus, 1, minus, start fraction, 1, divided by, 2, end fraction, b when a, equals, 12 and b, equals, 6.
=13a−1−12b=13⋅12−1−12⋅6        Replace a with 12 and b with 6.=4−1−3=0\begin{aligned} &\phantom{=}\dfrac13\blueD a-1-\dfrac12\goldD b \\\\ &= \dfrac13 \cdot \blueD {12}-1-\dfrac12 \cdot \goldD 6~~~~~~~~\text{Replace }\blueD{a} \text{ with } \blueD{12}\text{ and } \goldD b \text{ with } \goldD 6\text{.} \\\\ &=4 - 1 - 3 \\\\ &=0 \end{aligned}

Now, let's practice

Problem 1
  • Current
Evaluate start fraction, 3, divided by, 2, end fraction, y, minus, 3, plus, start fraction, 5, divided by, 3, end fraction, z when y, equals, 4 and z, 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

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