no 29 . luas daerah yg diarsir

[tex]l1 = \frac{1}{2} (8 \times 18) = 72 \: cm^{2} \\ l2 = \frac{1}{2} (8 \times 12) = 48 \: cm^{2} \\ l3 = \frac{1}{2} (8 \times 5) = 20 \: cm^{2} \\ [/tex]
Luas yang diarsir = (L1 + L2) - 2 L3
= (72 + 48) - 2 (20)
= 120 - 40
= 80 (C)