First thing you must always do is read the question slowly and a carefully taking note of all the numbers:
91 = age of Johnny
9 = age of jac
What the question is asking for is what amount of years would you get if you added both Johnny and Jac’s ages together:
Johnny is 91.
Jac is 9.
91 + 9 = 100
Thus, both of their ages together add up to 100!
Hope this helps! :)
