Luas yang diarsir adalah....

Luas segitiga I = 1/2 x 8 x 9 =36
L II = 1/2 x 12 x 9 = 54
L III = 2(1/2 x 9 x 2) = 18

L diarsir = (36+54) - 18
= 90 - 18 = 72