SOLUTION: Amy was born when Phil was 24 years old. When Amy is 3 times as old as she is today, Phil will be 3 times as old as Amy. How old is Phil today?

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Question 1059512: Amy was born when Phil was 24 years old.
When Amy is 3 times as old as she is today, Phil will be 3 times as old as Amy.
How old is Phil today?

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +a+ = Amy's age now
Let +b+ = Phil's age now
----------------------------
The difference in their ages will
ALWAYS be +24+ yrs
----------------------------
(1) +b+=+a+%2B+24+
----------------------------
Note that +3a+=+a+%2B+2a+
If I add +2a+ to Amy's age, I
must add it to Phil's, so this
is what I get:
----------------------------
(2) +b+%2B+2a+=+3%2A%28+a+%2B+2a+%29+
----------------------------
(2) +b+%2B+2a+=+9a+
(2) +b+=+7a+
----------------------
By substitution:
(1) +7a+=+a+%2B+24+
(1) +6a+=+24+
(1) +a+=+4+
and
(1) +b+=+a+%2B+24+
(1) +b+=+4+%2B+24+
(1) +b+=+28+
-------------------
Phil is 28 now
-------------------
check:
When Amy is 3 times as old as she is today, or
when she is +3%2A4+=+12+
Phil will be +12+%2B+24+=+36+
and +36+=+3%2A12+
OK