Tam N.

asked • 02/05/15

Linear equation, y = mx + b

Ann is 2x years old, and Dave is 3y years old. Ann is 3 times older than Dave. H2 years later, if you add Ann's and Dave's age together then you will get 28. What is Ann's and Dave's age?

Jon P.

tutor
Did you mean "2 years later?"  Or something else?
 
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02/05/15

Mark M.

What does "3 times older than Dave" mean? Three times Dave's age, or Dave's age plus three times his age?
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02/05/15

1 Expert Answer

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Edward C. answered • 02/05/15

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2x = 3(3y) = 9y
 
In 2 years, (2x+2) + (3y+2) = 28 so 2x + 3y = 24  
 
Plug in 9y for 2x in this equation to get 9y + 3y = 24  ==>  12y = 24  ==>  y = 2
 
Since 2x = 9y we have 2x = 18  ==> x = 9
 
Therefore Ann is 18 and Dave is 6.  
 
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Tam N.

Thanks so much for help. It's a fantastic way to solve the problem. By the way, do you recommend any book that helps in word problems. Thanks so much for help again.
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02/10/15

Edward C.

tutor
Sorry I don't know any books that specialize in word problems specifically.  Most algebra textbooks will have at least one or two sections on word problems.  The technique for solving most of them is pretty similar - you need to define the variables, then translate the words in the problem in to mathematical equations or inequalities that you can solve, and finally check that your answer is correct.  The best way to get better at solving word problems is to practice doing them.  There are lots of word problems posted here, you can try doing some of them and look at the answers if you need help.   
 
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02/11/15

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