The answer to a subtraction problem is called the difference.
My work is shown up above.
I think this is the answer.
The answer is 4 isn’t it?
2x+y+3=0
...................
9+10=?
9 = 3x3
10= 5x2
3 (from 3x3) x 5 (from 5x2) = 15
3 (from 3x3) x 2 (from 5x2) = 6
15+6=21
Therefore 9+10=21