13. A new CD costs $13.79, plus $0.97 in sales tax. How much do 3 new CDs cost? Explain how you found your answer.

The relationship between <7 and <8 can be said to be vertically opposite angles. They are equal to one another and formed by the intersection of two straight lines. i.e. the intersection of lines C and D.

The special angles created by the intersection of lines C and D can be used to solve for y because they all are inter woven and connected to one another either supplemtarily or by being vertically opposite angles.

5y - 29 = 3y + 19( vertically opposite angles)

5y - 3y = 19 + 29

2y = 48

y = 48/2

= 24.

<7 = <8

<7 + 5y - 29 = 180°( angles on a straight line)

<7 = 180° + 29 - (5 × 24)

= 209 - 120

<7 = 89°

<8 = 89° (vertically opposite angles)