Respuesta :

Formula for perimeter of rectangle = 2l + 2w

Substitute

40 = 2(7) + 2(x+2)
40 = 14 + 2x + 4
40 = 18 + 2x
22 = 2x
/2     /2
11 = x

Therefore 11 = x

Proof:

x + 2 = ?
11 + 2 = 13

13 + 13 + 7 + 7 = 40