<PRE><B>Question 825488</B>
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rates:
x = mary
y = bob
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x + y = 1/10
x = 1/15
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x + y = 1/10
1/15 + y = 1/10
y = 1/10 - 1/15
y = 15/150 - 10/150
y = 5/150
y = 1/30
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answer:
time = 1/r
1/y = 30 hours
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Solve systems of linear equations up to 4-equations 4-variables:
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