fiendex wrote:

Elena purchased Brand X pens for $4.00 apiece and brand Y for $2.80 apiece. If Elena purchased a total of 12 of these pens for $42.00, how many brand X pens did she purchase?

A) 4

B) 5

C) 6

D) 7

E) 8

Answer required is number of brand X pens. - An integer

Brand X pen costs $ 4.00

So total cost of required brand X pens will be integer (No of brand X pens * $ 4)

$42 - integer = integer

Hence, we are looking for a number when multiplied with $ 2.8 will give integer.

A quick look at options tells - 5 (12 - 7). So required answer brand X pens = 7

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