Question 460014
Always list what you know first.
p = perimeter
l = length
w = width
p = 2l + 2w
p = 2(l+w)
p = 90
.
The given relationship has to be turned from English into algebra.
.
length is 3 cm longer than twice the width
l = 2w + 3
.
Substitute and solve for l.
.
p = 2l + 2w
p = 2(2w+3) + 2w
p = 4w + 6 + 2w

90 = 6w + 6
84 = 6w
6w = 84
w = 84/6
w = 14 cm
.
Substitute this value to find l.
.
l = 2*w + 3
l = 2*14 + 3
l = 31 cm
.
Check the perimeter using
l = 31
w = 14
2(31)+2(14) = ??
62 + 28 = 90
Right.
.
Done