Answer:
A: 50
Explanation:
the answer is 50 because if the top line was even like the bottom line, then both the top and bottom line would equal 21 just like the bottom line. So if you do 21 minus 6 it would equal 15 which would be that line that doesn't have a number, so 15+6+21+8 all add up to 50. does that make sense?