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September 19, 2014

September 19, 2014

Posted by **Katherine** on Wednesday, November 10, 2010 at 5:02pm.

please help me....i need a chart or a rule to show me how u got it....please

- math -
**Mrs W**, Wednesday, November 10, 2010 at 6:12pmDo it this way

a=library books

b=textbooks

c=telephone books

You know a + b + c = 36

You know that a + b = 2b (library books plus textbooks equals twice number of textbooks)

You know that b + c = 3a (textbooks plus telephone books equals three times number of library books)

Take equation #2 a+b=2b

Subtract b from each side

a=b The number of library books equals the number of textbooks

Take equation #3 b+c=3a Substitute a for b since you know now from equation #2 that a=b Now you have a+c=3a

Subtract a from each side c=2a

Now, go to equation #1 a+b+c=36

You know a=b

You know c=2a

substitute

a + a + 2a = 36

Combine like terms and divide

4a = 36 a= 9

Again, you know a = b and c= 2a therefore a=9, b=9, c=18

9 library books

9 text books

18 telephone books

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