SOLUTION: Four years ago jane was twice the age of james. In four years from now james will be 3/4 the age of jane. How old is jane now?

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Question 433478: Four years ago jane was twice the age of james. In four years from now james will be 3/4 the age of jane. How old is jane now?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let a = Jane's age now
Let b = Jame's age now
given:
(1) +a+-+4+=+2%2A%28b+-+4%29+
(2) +b+%2B+4+=+%283%2F4%29%2A%28a+%2B+4%29+
-------------------------
(1) +a+-+4+=+2b+-+8+
(1) +a+-+2b+=+-4+
-----------------
(2) +b+%2B+4+=+%283%2F4%29%2Aa+%2B+3+
(2) +4b+%2B+16+=+3a+%2B+12+
(2) +3a+-+4b+=+4+
------------------
Multiply both sides of (1) by 2
and subtract (1) from (2)
(2) +3a+-+4b+=+4+
(1) +-2a+%2B+4b+=+8+
+a+=+12+
and
(1) +12+-+2b+=+-4+
(1) +2b+=+12+%2B+4+
(1) +2b+=+16+
+b+=+8+
12 is Jane's age now
8 is Jame's age now
check answer
(1) +a+-+4+=+2%2A%28b+-+4%29+
(1) +12+-+4+=+2%2A%288+-+4%29+
(1) +8+=+2%2A4+
+8+=+8+
OK
(2) +b+%2B+4+=+%283%2F4%29%2A%28a+%2B+4%29+
(2) +8+%2B+4+=+%283%2F4%29%2A%2812+%2B+4%29+
(2) +12+=+%283%2F4%29%2A16+
(2) +48+=+48+
OK