no 34 sama sama caranya yah...

Langsung aja y

BC = 18 cm
BD = 12 cm
BE = 18 - X
AB = 12 + X

AB / BE = BC / BD
(12+X) / (18-X) = 18 / 12
12(12+X) = 18(18-X)
2(12+X) = 3(18-X)
24 + 2X = 54 - 3X
2X + 3X = 54 - 24
5X = 30
X = 6

AB = 12 + X
AB = 12 + 6
AB = 18 cm

Jawabannya B

Semoga berguna +_+