all you do is multiply 9 and 2 first because those are your x and y then you multiply 2 and 3 because those are your x and z, then you subtract your first and last answers which is 18 and 6, the you got your answer which is 12.
U would add it even though it looks like u need to multiply but u don’t. In order to add, u need to find the lcd of them both which is 12. 10/12 + 9/12. 19/12 or 1 7/12.