Answer :
3 notebooks would be $3.15. You get this by doing 5.25 divided by 5 to get the cost for 1 notebook which is $1.05. Then you do $1.05 x 3= $3.15 because you are trying to find the cost of 3 notebooks.
You first need to divide 5.25 by 5 to get the price of one. This gives you 1.05. Then multiply it by 3. This gives you 3.15. There's you answer!