please dijawab beserta caranya

l = x
p = 5 + x

84 = (5 + x) * x
84 = 5x + x^2
0 = x^2 + 5x - 84
0 = (x + 12)(x - 7)
x = -12 / x = 7 (Pilih 7 karena panjang g mungkin minus)

l = 7
p = 5 + 7 = 12

k = 2 * (p + l)
   = 2 * (12 + 7)
   = 2 * 19
   = 38 cm (B)

keliling = 2 × ( p+l )
= 2 × ( 12 + 7 )
= 2 × 19
= 38

*maaf kalo salah