The perimeter of a rectangle is 20 ft. the width 8th 4 ft less than the length. find the dimensions of the rectangle

Perimiter is 20ft
width is
what
do you mean the width is  8 feet less than the length? or 4ft less?

anyway

P=2(L+W)
20=2(L+W)
divide by 2
10=L+W
and
L=10-W

width is 4ft less than length (I assuming)
W=-4+L
repalce W with -4+L
L=10-(-4+L)
L=10+4-L
L=14-L
2L=14
L=7
W=-4+L
W=-4+7
W=3

it is 7ft by 3ft