Mary purchased Brand X pens for $2 apiece and brand Y for $1 apiece. If Elena purchased a total of 12 of these pens for $20.00, how many brand X pens did she purchase?
Choose the correct choice from the following
A) 8  B) 9  C) 5  D) 4  E) 6
2x+y=20 -only one positive integers solutions x=8 and y=4   8nswer is 8
<result>A</result>
Mary purchased Brand X pens for $2 apiece and brand Y for $1 apiece. If Elena purchased a total of 12 of these pens for $20.00, how many brand X pens did she purchase?