X = 4
If they are equal to one another set them in an equation equal to one another
4x-7 = -x+13
Add x on both sides to get the variables together and add 7 on both sides to get the variables alone
4x+x-7+7 = -x+x + 13 + 7
Simplify
5x = 20
Divide by 5 on both sides
5x/5 = 20/5
Simplify
X = 4