Ineed with all of these i don’t get it

The first question each friend gets 1/8 of the whole pizza 
for half of the pizza each friend gets 1/4 so that times 2 equals 1/8

The second question one person gets 1/15 of the brownie pan
1/5 times 3 equals 1/15
 
The third question 1/3 cup one serving 1 cup three servings three times six equals 18 servings 

The fourth question 1/5 cup one muffin one cup 5 muffins five times nine equals forty-five muffins

Hope this helps

Two because two of one thing is two.