The art teacher has 30 boxes of crayons with 16 cans in each box she gives the students 10 of the boxes to use explain how to find the number of crayons that the teacher has left

I'm going to assume you meant crayon instead of can:

First step is to find how many boxes she/he has left.

30 - 10 = 20 

So the teacher has 20 boxes left;

Now, knowing that each box has 16 crayons, then we simply multiply the 20 by 16 to find the total number of crayons left over:

20 x 16 = 320 

So the art teacher has 320 crayons left over.

Hope this helps!