Ms Yost has 20 boxes of markers. Next year, she plans to buy 420% more boxes. How many boxes will she have in all?

She will have 104 boxes.

Step-by-step explanation:

Thing of it like this:

100% of 20 is 20, so 400% would be 80. Then the last 20% could be answered like this:

divide 20 by 10. Since it is 20%, multiply by 2. You get 4. Add the sums to get 104. The reason you divide 20 by 10 is because its easier and since 2x10 is 20, then 20/10 is reasonable.

step-by-step explanation: you take each of the numbers and divide by the amount then you take the range