# algebra

posted by
**Neil** on
.

John has 36 books in his locker.

He has text books,library books, and telephone books. How many books of each kind does he have if:

lib + tel= 2x text books and

text + tel = 3x lib books

I think it'd be easier to let T,L and B denote text books, library books and telephone books. Then

(1) L + B = 2T

(2) T + B = 3L

We also know

(3) T + L + B = 36

So from (1)

L = 2T - B now substitute into (3) to get

T +2T - B + B = 36 or

3T = 36 so

T = 12, therefore L + B = 24 or L = 24 - B

Then from (2)

12 + B = 3(24 - B) so

12 + B = 72 - 3B and

4B = 60 or B = 15

You should be able to figure out what L is and verify if the answers are correct.