Answer :
Call the length a, the width b
Perimeter = (a+b) x 2
We have : a - b = 4 and (a+b) x 2 = 56
-> a + b = 28
-> a - b = 4
=> a+b + (a-b) = 32
2a = 32
a = 16
b = 56:2-16 = 12
So, the length = 16 and the width = 12
Call the length a, the width b
Perimeter = (a+b) x 2
We have : a - b = 4 and (a+b) x 2 = 56
-> a + b = 28
-> a - b = 4
=> a+b + (a-b) = 32
2a = 32
a = 16
b = 56:2-16 = 12
So, the length = 16 and the width = 12