so lets start with making these equations
x + y = 43
x - y = 7
now we can rewrite the second equation in terms of x
x = 7 + y
now we plug that x value back into the first equation
7 + y + y = 43
7 + 2y = 43
2y = 36
y = 18
now we can plug the value of y into the rewritten second equation leaving us with
x = 7 + 18
x = 25
so y = 18 and x = 25
and the difference is 7
please give brainliest!