Set them both equal to 104°
7x+30+9x+42=104
Combine like terms
16x+72=104
Subtract 72 from both sides
104-72=32
16x=32
Divide by 16 on both sides
32/16=2
x=2
Plug it in for the measure of angle BOC:
9(2)+42
18+42=60
Measure of angle BOC is 60°
