tolong dong yg baik bantu saya gimana cara nya carinya? mks.. :)

L △1 = 1/2 × 10 × 12 = 60
L △2 = 1/2 × 10 × 18 = 90
L daerah yg diarsir = 1/2 × 10 × 5 = 25
L daerah yg tdk diarsir
= ( 60 - 25 ) + ( 90 - 25 )
= 35 + 65
= 100