SOLUTION: jack is 3 years older then his sister jill. the sum of their ages is 45. how old are jack and jill.

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Question 627189: jack is 3 years older then his sister jill. the sum of their ages is 45. how old are jack and jill.
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +a+ = Jack's age now
Let +b+ = Jill's age now
given:
(1) +a+=+b++%2B+3+
(2) +a+%2B+b+=+45+
-------------------
Substitute (1) into (2)
(2) +b+%2B+3+%2B+b+=+45+
(2) +2b+%2B+3+=+45+
(2) +2b+=+42+
(2) +b+=+21+
and, since
(2) +a+%2B+b+=+45+
(2) +a+%2B+21+=+45+
(2) +a+=+24+
Jack is 24 and Jill is 21