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Big Ideas Math Geometry, 2014

BI

Big Ideas Math Geometry, 2014 View details

Maintaining Mathematical Proficiency

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Exercise 12 Page 461

Solve for the variable by using the Cross Products Property.

$x = 17$

Practice makes perfect

To solve the proportion, we will start by using the Cross Products Property. Remember that we will need to treat

3 x - 15

as a single quantity in the cross multiplication process.

\frac{9}{3 x - 1 5} = \frac{3}{1 2}

Cross multiply

9 \cdot 12 = (3 x - 15) \cdot 3

Multiply

108 = 3 (3 x - 15)

Rearrange equation

3 (3 x - 15) = 108

From here, we will continue solving for

x

by using the Distributive Property and the Properties of Equality.

3 (3 x - 15) = 108

Distribute $3$

9 x - 45 = 108

$LHS + 45 = RHS + 45$

9 x = 153

$LHS / 9 = RHS / 9$

x = 17

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Exercises p.461