let length be l
and breadth be b
perimeter = 28
2(l+b) = 28
l + b = 14
l = 14 - b
area = 48
l x b = 48
(14 - b) b = 48
14b - b^2 = 48
b^2 - 14b + 48 = 0
b^2 -6b - 8b + 48 = 0
b( b - 6 ) - 8 ( b - 6) = 0
(b-8) ( b-6) = 0
so
either b = 8 or b = 6
if b= 8
l = 14 - 8 = 6
( not possible as length cannot be smaller than breadth)
so
breadth = 6
length = 8
