Nine books

Nine books are to be bought by a student. Art books cost $6.00 each, and biology books cost $6.50 each. If the total amount spent was $56.00, how many of each book were bought?

Correct answer:

a =  5
b =  4

Step-by-step explanation:


a+b = 9
6a + 6.5b = 56.00

a+b = 9
6·a + 6.5·b = 56.00

a+b = 9
6a+6.5b = 56

Pivot: Row 1 ↔ Row 2
6a+6.5b = 56
a+b = 9

Row 2 - 1/6 · Row 1 → Row 2
6a+6.5b = 56
-0.08b = -0.33


b = -0.33333333/-0.08333333 = 4
a = 56-6.5b/6 = 56-6.5 · 4/6 = 5

a = 5
b = 4

Our linear equations calculator calculates it.



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