let length be X, and width be Y
From the question,
2(X+Y)=52---------(1)
(X+4)Y/2=XY+60-------(2)
Combing the two equation,
(X+4)(26-X)/2=X(26-X)-60
(X+4)(26-X)=2X(26-X)-120
-X^2+22X+104=-2X^2+52X-120
X^2-30X+224=0
(X-14)(X-16)=0
X=14 or 16
Hence Y=12 or 10