Đáp án đúng: C
Giải chi tiết:\(\eqalign{& 165 - (35:x + 3).19 = 13 \cr & (35:x + 3).19 = 165 - 13 \cr & (35:x + 3).19 = 152 \cr & 35:x + 3 = 152:19 \cr & 35:x + 3 = 8 \cr & 35:x\,\,\,\,\,\,\,\,\,\, = 8 - 3 \cr & 35:x\,\,\,\,\,\,\,\,\, = 5 \cr & \,\,\,\,\,\,\,\,\,x\,\,\,\,\,\,\,\,\, = 35:5 \cr & \,\,\,\,\,\,\,\,\,x\,\,\,\,\,\,\,\,\, = 7 \cr} \)
vậy x =7