SOLUTION: A teacher bought 20 books in a sale. Some cost £8 each and the others cost £3 each. She spent £110 in all. How many of the £3 books did she buy? Let x be the number of £3 boo

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: A teacher bought 20 books in a sale. Some cost £8 each and the others cost £3 each. She spent £110 in all. How many of the £3 books did she buy? Let x be the number of £3 boo      Log On


   

Question 734088:
A teacher bought 20 books in a sale. Some cost £8 each and the others cost £3
each. She spent £110 in all. How many of the £3 books did she buy? Let x be
the number of £3 books she bought
Answer by checkley79(3341) About Me  (Show Source):
You can put this solution on YOUR website!
X+Y=20
X=20-Y
3X+8Y=110
3(20-Y)+8Y=110
60-3Y+8Y=110
5Y=110-60
5Y=50
Y=50/5
Y=10 NUMBER OF 8 DOLLAR(?) BOOKS.
X=20-10=10 NUMBER OF 3 DOLLAR (?) BOOKS.
PROOF:
3*10+8*10=110
30+80=110
110=110