tolong bantu pake cara ya...

Ditanya = Besar sudut ABD

<ABD + <DBC = 90°

(6x + 13)°+ (3x - 4)° = 90°
9x + 9 = 90
9x = 90-9
9x = 81
x = 9

Besar <ABD = 6x + 13 --- 6×9 + 13

54 + 13 = 67 (c)