Answer:
31
Step-by-step explanation:
3x + 12 and 105 are alternate exterior angles because A || B and B || C.
If the two or more lines are parallel, then the alternate exterior angles are equal.
3x + 12 = 105
Substract 12 on both sides,
3x = 105 - 12
3x = 93
Divide 3 on both sides,
x = 93 / 3
x = 31
