Respuesta :

Answer:

x = 8

Step-by-step explanation:

The perimeter (P) is calculated as

P = 2(l + b) ← l is length and b is breadth

Here l = 12 and b = x , P = 40, then

2(12 + x) = 40 ( divide both sides by 2 )

12 + x = 20 ( subtract 12 from both sides )

x = 8