Missing measure in each formula?

Question

w=7, L=12, P=?

w=15.5, P=81, L=?

Thanks so much for your help! :D

Answer 1

P = 2L + 2W

1) P = 2(7) + 2(12) = 14 + 24 = 38

2) 81 = 2(15.5) + 2L

81 = 31 + 2L

2L = 50

L = 25

Answer 2

Yes, I'm making the same assumptions your first contributor did:

L = length, W = width, P = perimeter

P = 2L + 2W

1./ P = 2L + 2W

     P = 2(12) + 2(7)

     P = 24 + 14

     P = 38

2./ P = 2L + 2W

     2L = P - 2W

      L = (P - 2W)/2

      L = (81 - 31)/2

      L = 25

Proof  2(25) + 2(15.5) = 81

           50 + 31 = 81