Question 153262
Sarah's age exceeds Judy's age by 16 years. Four years ago, Sarah was twice as old as Judy. Find there ages now. 
---------
S = Sarah's age now
J = Judy's age now
S = J + 16  (it says that)
Four years ago, Sarah was 2 times Judy's age:
S-4 = 2*(J-4)
-------
Substitute for S
S-4 = 2*(J-4)

(J+16) - 4 = 2*(J-4)
J+12 = 2J-8
J+20 = 2J
20 = J
------
S = J+16, so S = 36