Stacy made 3 dozen oatmeal cookies. she ate 1/6 of them. how many did she have left?

Given:
3 dozen oatmeal cookies
1/6 of them was eaten

How many was left?

1 dozen is equal to 12 pieces. 
3 dozen * 12 = 36 pieces
36 * 1/6 = 36/6 = 6

Stacy ate 6 pieces of oatmeal cookies.
36 - 6 = 30 pieces left.

There are 30 pieces of oatmeal cookies left.

The only number less than 8 that can equal 12 would be 6, 36 is the dividend