SOLUTION: Three years ago the average age of A and B was 18 years. While C joining them now, the average becomes 22 years. How old (in years) is C now?

Question 942477: Three years ago the average age of A and B was 18 years. While C joining them now, the average
becomes 22 years. How old (in years) is C now?
Answer by macston(5194) (Show Source): You can put this solution on YOUR website!
If three years ago the average was 18, today the average is 21 so
(A+B)/2=21
A+B=42
with C the average is 22 so
(A+B+C)/3=22
A+B+C=66 Substitute A+B from above
(A+B)+C=66
42+C=66 subtract 42 from each side
C=24 so C is currently 24 years old
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