Answer: 3 packages and 3 leftover
Explanation:
We will subtract 6 (in a package) from 21 (how many she ate) to find out how many packages she ate and how many she has left.
21 - 6 - 6 - 6 = 3
It took 6 three times (18) so she ate three packages and she has 3 leftover.
We can also write an equation to represent this, where x is the number of packages
21 - (6x) = 3