Your English grammar needs attention before you can solve this problem.
Sentences begin with a capital letter and end with a period.
Questions start with a capital letter and end with a question mark.
"the sum between ..." is certainly non-standard terminology, but I think you mean "the sum of:.
Now the problem:
x-y=45
3x+2y=10
3(45+y)+2y=10
You solve it from here.