SOLUTION: four years ago SOPHIE WAS twice as old as her sister. right now she is 1.5 times older than her sister. how old is sophie right now

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Question 796970: four years ago SOPHIE WAS twice as old as her sister. right now she is 1.5 times older than her sister. how old is sophie right now
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +a+ = Sophie's age now
Let +b+ = her sister's age now
----------------------------
(1) +a+-+4+=+2%2A%28+b+-+4+%29+
(2) +a+=+%283%2F2%29%2Ab+
-----------------
Substitute (2) into (1)
(1) +%283%2F2%29%2Ab+-+4+=+2%2A%28+b+-+4+%29+
(1) +%283%2F2%29%2Ab+-+4+=+2b+-+8+
(1) +3b+-+8+=+4b+-+16+
(1) +b+=+16+-+8+
(1) +b+=+8+
and
(2) +a+=+%283%2F2%29%2A8+
(2) +a+=+12+
Sophie is 12 now
check:
(1) +a+-+4+=+2%2A%28+b+-+4+%29+
(1) +12+-+4+=+2%2A%28+8+-+4+%29+
(1) +8+=+2%2A4+
(1) +8+=+8+
OK