If x= 5 when y= 12 find x when y = 30
Area = 420 sq m
length x breadth = 420
(l + 7)(b -5) = 420
lb = (l+7)(b-5)
lb = lb - 5l + 7b - 35
-5l + 7b - 35 = lb - lb
7b - 5l = 35
7b = 35 + 5l
b = = 5 + m
-5l = 35 - 7b
l = = - 7 m