If each pencil is $0.25 each, and you purchase 30 pencils, then the equation is:
0.25 x 30 = $7.5
$11 - $7.5 = $3.5
This means you have 3.5 dollars to spend on pens.
If each pen is $2, you only have enough money to buy one pen.
Remaining money: $1.5
Total money spent: $9.5
Hope this helps! Good luck.