Answer:
Son's Age: 11
Mary's Age: 33
Step-by-step explanation:
Let set Mary and her son as variables,
M = Mary's age
S = Mary's son age
Breakdown:
"Mary is three times as old as her son"
M = 3S
"In 12 years, Mary's age will be one less than twice her son's age"
M + 12 = 2(S + 12) - 1
we add 12 to both sides as it will be in 12 years for both
We know that M = 3S, so we plug this in
3S + 12 = 2(S + 12) - 1
Now solve for S (son's age),
3S + 12 - 12 = 2(S + 12) - 1 - 12
3S = 2(S + 12) - 13
3S = 2S + 24 - 13
3S - 2S = 2S - 2S + 24 - 13
S = 24 - 13
S = 11
To find Mary age, plug in her son age ,
M = 3S
M = 3(11)
M = 33
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