At the start of school year, Mario stocked up on school supplies, which included lined filler paper and number two wood pencils.
He bought three packs of paper and two boxes of pencils for a total cost of $3.25. Two months later he was running low on supplies, so he bought two more packs of paper and one more box of pencils for a total of $2.00. Assuming that prices for the school supplies remained the same, what was the price of one pack of paper and one box of pencils?
<span>Let Y be the price for a box of pencils. </span>
<span>1) X * 3 packs + Y * 3 boxes = $3.25 </span>
<span>2) X * 2 packs + Y * 1 box = $2.00 </span>
<span>Re-arranging equation 2) gives you Y = ($2.00 - X * 2 packs) / 1 box </span>
<span>Subsitute Y for the Y term in equation X. Multiply through the bracket, collect like terms and solve for X. Then you can use either equation to solve for Y (if you don't get the same answer, you've made a mistake).</span>
Divide the 90 stamps by 45: The result is 2; it's equal to 1% of the total number of stamps. You then multiply it by 100 to get the full amount, which is 200 stamps.
