Rachel and tarah buy a pizza that is cut into 8 equal pieces. if rachel eats 1/8 of the pizza and tarah eats 1/4 of the pizza, how many eighths of the pizza are left?

Convert 1/4 into 8ths. To do this, multiply the top and bottom by 2.
1/4 = 2/8. Now you add the piece Rachel ate to get 3/8. You want to know how much is left so subtract 3/8 from 8/8.
8-3=5. There are 5/8 of the pizza left.

We want to find it in eighths

convert to eitghts
1/4 times 2/2=2/8

at first there are 8/8 pizza
then 1/8 is eaten
then 2/8 is eaten

8/8-1/8-2/8=7/8-2/8=5/8

5 eighths of the pizza are left