Write two expressions whose sum is x - 3 / x + 2
this is rational expressions by the way

I'm assuming the given expression is (x-3)/(x+2)

One way to break that down into the form A+B, where A and B are rational expressions, is to have
A = x/(x+2)
B = -3/(x+2)

The numerators x and -3 are added to get x-3 and the result is placed over the LCD (lowest common denominator)