Saya butuh bantuan bgt please para prof matematic

EF = (AD . BE + BC . AE) / AB
12 = (9 . 4 + 14 . x) / (4 + x)
12(4 + x) = 36 + 14x
48 + 12x = 36 + 14x
14x - 12x = 48 - 36
2x = 12
x = 12/2
x = 6

jawaban A