Question

A flat rectangular piece of aluminum has a perimeter of 66 inches. The length is 15 inches longer than the width. Find the width.

Answer 1

x is the length
y is the width
2x+2y=66
x-y=15
multiply the second equation by 2 (elimination)
2x-2y=30
add the equations together
4x=96
x=24
Plug this in to one of the original equations
24-y=15
the width is 9