Question

the length of a rectangular building is 6 feet less than 3 times t he width. The perimeter is 120 feet. Find the width and the length of the building.

Answer 1

Call the width x.  Note that the length is 3x-6.  We know that double the width plus double the length is 120, so we write an equation:

$2(x)+2(3x-6)=120$
$2x+6x-12=120$
$8x-12=120$
$8x=132$
$x=16.5$
If x is 16.5, the width is 16.5, and the length is $3 \cdot 16.5 - 6 = 43.5$.