B.
When two lines intersect they form two pairs of opposite angles.
Vertical angles are always congruent, which means that they are equal.
so m<7 = m<8 or m<3y + 19 = m<5y-29
C. solve for y and measure <7 and <8
3y + 19 = 5y-29
5y - 3y = 19+29
2y = 48
y = 24
so
5y-29 = 5(24) - 29 = 91
3y + 19 = 3(24) + 19 = 91
so <7 = 180 - 91 = 89
<7 = <8 = 89