nomor 4!!! tolong pakai cara yaaa!

a. = 1/2×3×4
    = 6 cm2
b. = [2×6]+[(3+4+5)×9]
    = [2×6]+[12×9]
    = 12+108
    = 120 cm2
c. = 6×9
    = 54 cm3

Maaf kalau gak jelas!!!