Question 315712
The length, L, can be expressed in terms of the width, W, thus:
1) L = 2W+3 "...the length ...is 3cm longer than twice the width..."
The perimeter of a rectangle is given by:
2) P = 2L+2W  
a) Substitute equation 1) for L in equation 2)
2(2W+3)+2W = P Simplify.
4W+6+2W = P
6W+6 = P or {{{highlight(P = 6W+6)}}}
b)  Substitute P = 90 and solve for W.
6W+6 = 90 Subtract 6 from both sides.
6W = 84 Divide both sides by 6.
W = 14 and...
L = 2W+3
L = 2(14)+3
L = 31
Length = 31cm.
Width = 14cm.