Rectangle has area=168 m^2 and diagonal of 25. Find length

This is how tried to attempt the problem

Area= L X W

168 = L x W ..........(1)

L^2 + W^2 =25^2 ............(2)

From (1) L = 168/W...........(3)

Substitute (3) into (2)

(168/W)^2 +W^2 = 625

28224/W^2 + W^2 = 625

The problem gets complicated as I proceed

Is this aproach correct if it is,

Is there a convinient method