Dustin bought 9 pencils. Some of the pencils were green and cost $0.90 each. The remainder of the pencils were purple and cost $0.65 each. If Dustin paid $7.10 for all of the pencils, how many green pencils did he buy?

Answer: he bought 5 green pencils

Step-by-step explanation:

Let x represent the number of green pencils that Dustin bought.

Dustin bought 9 pencils. The remainder of the pencils were purple. This means that the number of purple pencils that he bought is 9 - x

Some of the pencils were green and cost $0.90 each. The remainder of the pencils were purple and cost $0.65 each. If Dustin paid $7.10 for all of the pencils, it means that

0.9x + 0.65 (9 - x) = 7.1

0.9x + 5.85 - 0.65x = 7.1

0.9x - 0.65x = 7.1 - 5.85

0.25x = 1.25

x = 1.25/0.25

x = 5