Question 973149
Let Jerry's present age be x.
Let Joel's present age be y.
We have x+y=36.........equation 1
Nine years ago, Jerry was twice as old as Joel.
x-9=2(y-9)
x-9=2y-18
x=2y-9..............equation 2
Substituting equation 2 in equation 1 we get,
2y-9+y=36
3y-9=36
3y=45
y=15
Substituting in equation 1 we get,
x=21.
Jerry's age is 21 and Joel's age is 15 years old.