What two numbers whose sum is 111 and whose difference is 43?
This is easily solved by using two equations in 2 unknowns and
solving the system.
x + y = 111
x - y = 43
If have not yet had the pleasure of studying algebra and the
answer is important to you, you could hope the numbers are positive
integers and try all pair of numbers whose sum is 43:
1,42
2,41
3,40 and so on, until you find a pair whose difference is
43.