SOLUTION: solve the equation the ages of a and b are in ratio 5:7.four years from now the ratio of their ages will be 3:4 . the present age of b is

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Question 568959: solve the equation the ages of a and b are in ratio 5:7.four years from now the ratio of their ages will be 3:4 . the present age of b is
Answer by scott8148(6628) About Me  (Show Source):
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5b = 7a

3(b + 4) = 4(a + 4) ___ 3b + 12 = 4a + 16 ___ 21b + 84 = 28a + 112

subtracting 4 times first eqn ___ 21b + 84 - 20b = 28a + 112 - 28a ___ b = 28