Analysis: According to the meaning of the question, the solution of equation 5a+x= 13 is x=-2, so we can find a=3 first, and then substitute it into the original equation to solve it.
Answer:
Solution: From the meaning of the question, 5a-2= 13,
Solution, a=3,
∴ The original equation is 15-x= 13,
Solution, x = 2;;
So choose C.