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Big Ideas Math: Modeling Real Life, Grade 7
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Big Ideas Math: Modeling Real Life, Grade 7 View details
3. Solving Two-Step Equations
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Exercise 3 Page 140

Start by adding 12 to both sides.

x=7

Practice makes perfect

To solve an equation, we should first gather all of the variable terms on one side and all of the constant terms on the other side using the Properties of Equality. In this case, the only variable term is already on the right-hand side of the equation, so we will start by adding 12 to both sides.

9=3x-12
AddEqn

LHS+12=RHS+12

9+12=3x-12+12
AddTerms

Add terms

21=3x
DivEqn

.LHS /3.=.RHS /3.

21/3 = 3x/3
CalcQuot

Calculate quotient

7=x
RearrangeEqn

Rearrange equation

x=7

The solution to the equation is x=7. We can check our solution by substituting it into the original equation.

9=3x-12
Substitute

x= 7

9 ? = 3( 7)-12
Multiply

Multiply

9 ? = 21-12
SubTerm

Subtract term

9=9

Since the left-hand side is equal to the right-hand side, our solution is correct.

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arrow_right Try It p.140-141
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Try It 2 (Page 140)
Try It 3 (Page 140)
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Try It 7 (Page 141)
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Try It 9 (Page 141)
arrow_right Self-Assessment for Concept & Skills p.141
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Self-Assessment for Concept & Skills 11 (Page 141)
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arrow_right Self-Assessment for Problem Solving p.142
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arrow_right Review & Refresh p.143
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