Question

Scott ate half of the pizza.
How many pieces did he eat?

Answer 1

Assuming the pizza has 8 slices, eating half (50%/0.50) of the pizza would be 4 slices.
If the pizza has a different amount of slices then just split that number in half, you can do so by dividing it by 2, multiplying it by 0.5 or taking away so many that the amount left is the same amount that you took away.

Answer 2

If Scott ate half of the pizza, it means he ate 50% of the pizza. To determine how many pieces he ate, you would need to know the total number of pieces in the pizza. If you provide the total number of pieces, I can tell you how many pieces Scott ate.