The sum of two numbers is 10. if one number is subtracted from the other the result is -2. find two numbers

Form an equation to describe the situation
x+y=10 
Then use the other information they gave you and form another equation
x-y=2
You can add the two equations together, and you see that the y variables cancel out(elimination)
2x=12
Solve for one variable and then plug it back into the original equation
x=6
6+y=10
y=4