Question 1145713
The sum of Sam and Mary's age is 60.
s + m = 60
m = (60-s)
 Twelve years ago, Sam was three times as old as Mary.
s - 12 = 3(m-12)
s - 12 = 3m - 36
s = 3m - 36 + 12
s = 3m - 24
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1. Write a system of equations to represent this situation.
in the above equation, replace m with 60-s
s = 3(60-s) - 24
s = 180 - 3s - 24
s + 3s = 180 - 24
4s = 156
s = 156/4
s = 39 yrs is sam's age
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2. Find Mary's age now
60 - 39 = 21 yrs is Mary's age
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See if that checks out
39 - 12 = 3(21-12)
27 = 3(9)