How many pencils did Serena buy?

Question

Serena bought a total of 135 notebooks and pencils for her students. Each notebook cost $1.75, and each pencil cost $0.35. The total cost of her purchase was $122.85.

How many pencils did Serena buy?

Answer 1

Let x = the number of pencils Serena bought

Let 135 - x = the number of notebooks Serena bought

1.75(135 - x) + .35x = 122.85       Multiply both sides of this equation by 100.

175(135 - x) + 35x = 12,285

23,625 - 175x  + 35x = 12,285

-140x = -11,340

x = 81 pencils