Answer:
<18 = 40
Explanation:
<3 = <19 since they are alternate exterior angles and alternate exterior angles are equal for parallel lines cut by a transversal
<19 = 140
<19+<18 = 180 since they form a straight line
140 + <18 = 180
Subtract 140 from each side
140-140 + <18 = 180-140
<18 = 40