keliling sebuah segitiga 90cm jika selisih panjang dan lebarnya 12cm luasnya adalah...?

K = 90
p-l = 12
p = 12 + l
p = a , l = t

K = a + b + c = 90
12 + b + c = 90
b + c = 90 - 12
b,c = 78 : 2
b,c = 39
t = 39

a = 12 + t
a = 12 + 39
a = 51

L = a x t : 2
= 51 x 39 : 2
= 994,5