plis tolong nomor 56 kak, makasih :)

t △ABC = 6 - x
t △ADE = x

BC/DE = 6 - x / x
6 / 3 = 6 - x / x
6x = 18 - 3x
6x + 3x = 18
9x = 18
x = 18/9
x = 2

L △ABC + L △ADE
= ½ × a × t + ½ × a × t
= ½ × 6 × (6-2) + ½ × 3 × 2
= 12 + 3
= 15 cm² (B.)