Amy sold pens and pencils for a fundraiser at school. Pencils sold for $1.50 and pens sold for $2. She sold a total of 35 items and made $61.50. How many pens did Amy sell?

Let's break this down into a system of equations.

Let d = number of pencils, and p = number of pens.

We want to solve for p.

These are our two equations:

1) 1.50d + 2p = 61.50.

She sold $61.50 in merchandise, $1.50/pencil, $2/pen

2) d + p = 35

She sold a total of 35 items.

To solve for p, let's write equation p a different way:

3) d = 35 - p

Now we can substitute d from equation 3) into equation 1) to figure out the answer.

1.50 (35 - p) + 2p = 61.5

52.5 - 1.5p + 2p = 61.5 Distribute within parentheses

52.5 +.5p = 61.5 Subtract 52.5 from each side

.5p = 9 Multiply both sides by 2

p = 18

p = 18

Amy sold 18 pens. To find how many pencils she sold:

p + d = 35

18 + d = 35

d = 17

Answer is 18 pens.