Jed is 25 - 10 = 15 years old now. So, Matt is 15 - 10 = 5 years old now. Thus, the sum of their present ages is 15 + 5 = 20.
This justifies what answer for what question? Q & A:
Jed is 10 years older than Matt. In 10 years, Jed will be 25 years old. What is the sum of their present ages?
20