4. Multiple-Choice 1. Two complementary angles measure (12r - 18)° and (5x + 23)°. What
is the measure of the smaller angle?
(1) 5°
(2) 42°
(3) 48°
(4) 90°

I already know that the answer is 42 but I don’t know how to get that! Please help.

(2) 42°

Step-by-step explanation:

Copy of the given problem:

4. Multiple-Choice

1. Two complementary angles measure (12r - 18)° and (5x + 23)°. What

is the measure of the smaller angle?

(1) 5°

(2) 42°

(3) 48°

(4) 90°

Solution:

The sum of the measures of complementary angles is 90 deg.

12r - 18 + 5x + 23 = 90

We have 1 equation with two different variables, so we cannot solve the equation to find unique values of the variables.

I assume the above is an error, and both variables should be the same.

12r - 18 + 5r + 23 = 90

Combine like terms on the left side. Terms with r are combined. Terms with no variable are combined.

12r + 5r - 18 + 23 = 90

17r + 5 = 90

Subtract 5 from both sides.

17r = 85

Divide both sides by 5.

r = 5

The measures of the angles are:

12r - 18 = 12(5) - 18 = 60 - 18 = 42

5r + 23 = 5(5) + 23 = 25 + 23 = 48

The measures of the two angles are 42°  and 48°.

The smaller angle measures 42°

(2) 42°

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step-by-step explanation: