Answer:
x+10-y
Step-by-step explanation:
i'm not 100% sure about this response, but i'd assume the answer is like this for the following reasons:
alex is x years old, and 10 years have passed, meaning 10 years are added onto his age (x+10). addison is still the same amount of years apart from him in age, so you subtract y from that (x+10-y).
