Respuesta :

P = 2l + 2w
P = 2(x + 3) + 2(7)
P = 2(x) + 2(3) + 14
P = 2x + 6 + 14
P = 2x + 20

A = lw
A= 7(x + 3)
A = 7(x) + 7(3)
A = 7x + 21