tolong jawab soal ini yy

K = 2p + 2l.
80 = 2(2x - 3) + 2(x + 7).
80 = 4x - 6 + 2x + 14.
80 = 6x + 8.

6x = 80 - 8.
6x = 72.
x = 72/6.
x = 12.

Jawaban : C.

keliling = 80cm
2(p+l) = 80
(p+l) = 80/2
(2x-3) + (x+7) = 40
2x+x+7-3=40
3x+4 = 40
3x= 40-4
3x=36
x=36/3
x= 12

jadi nilai x = 12