Assume the Width of the rectangle = W cm
Length of the rectangle = W+4 cm
Area of the rectangle = 165 cm2 => W(W+4) = 165
W2 + 4W -165 =0
W2 + 15W -11W -165 =0
W(W+15) - 11(W+15) =0
(W+15)(W-11) = 0
W = 11 cm
Hence the width of the rectangle is 11 cm.