=================================
Explanation:
10x and -8x are like terms. Subtract them to get 2x. Think of it as having 10 xrays and then you take away 8 xrays, so you're left with 2 xrays. In shorthand we would say 10x-8x = 2x. We subtract the 10 and 8 to get 2, then tack on x afterward.
The other pair of like terms are the 2 and 10 which simply add to 2+10 = 12 like normal
