<PRE><B>Question 1052923</B>
The sum of the ages:
J+M = 32 Subtract M on both sides
J = 32-M (1)
Four years ago John was 2*Mary:
J-4 = 2(M-4) (2)
In equation (2) substitute the value of J per (1):
32-M-4 = 2M-8
28-M = 2M-8
36-M = 2M
36 = 3M flip the equation so we have the unknown of the left
3M = 36 divide both sides by 3
M = 12
and J = 32-M = 32-12 = 20
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Check
20-4 = 2(12-4)
16 = 16 correct</PRE>