Question 175973
In 1987, Joy was 3 times as old as Ali. If Ali was born 8 years after Joy, what age will each be in 1999? 
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a = Ali's age in 1999
j = Joy's age in 1999
j = a + 8  (Joy was born 8 years after)
In 1987:
j-12 = 3*(a-12) (Joy was 3x Ali's age 12 years ago)
j-12 = 3a-36
Sub a+8 for j
(a+8) - 12 = 3a-36
a-4 = 3a-36
-2a = -32
a = 16 (in 1999)
j = 24 (in 1999)