Answer:
Jeff ate 4 slices of pizza
Explanation:
First off, let's find how many total slices there are in 5 pizzas.
We know that each pizza has 8 slices, and that Jeff ordered 5 pizzas in total.
Total Slices = 5 pizzas * 8 slices = 40 slices
Let's rewrite the percentages as fractions to make things a little easier:
60% = 6/10
25% = 1/4
Now, lets find out how many slices were left after the party:

Now all we need to do is find 25% or 1/4 of 16:

Therefore, Jeff ate 4 slices of pizza!