Acompany buys paper clips at the rate of $7.50 per box for the first 10 boxes, $5.50 per box for the next 10 boxes, and $3.50 per box for any additional boxes. how many boxes of paper clips can be bought for $221.00?

46 boxes

Step-by-step explanation:

So for a total of 20 boxes, the cost is

We have remaining

Each additional box costs 3.5, so for 91 dollars, we can get:

boxes

So, total boxes can be bought for $221.00

expression #3 is not equivalent. the others are.