<span>B) 84 + z = 180, since 42*2=84, 180-84=96, z=96</span>
First, realize that angle ABC is the sum of the two other angles. Hence, form an equation in which you subtract the measure of one of the angles from angle ABC to get the measure of the other angle -- the one you are solving for.
2x + y = 10
5x - y = 18
7x = 28
x = 4
2(4) + y = 10
8 + y = 10
y = 2
(4,2)
