Plates needed=(b+c)/p Let's say she has a total of 70 buns and cookies. And she wants to put 5 of one or the other on each plate. Then, she needs 70/5, or 14 plates ☺☺☺☺

Ok, we have C cookies, B buns, and she wants to put P things in each plate.

The number of plates can be obtained by:

(C + B)/P = N

Where you divide the total number of things (cookies + buns) into the number P, that is the number that goes in each plate, and in this way, you find how many groups of P things there are, and that number of groups is equal to the number of plates needed.