To find out the unit rate
Divide the number of teaspoons by the total cups
so
If the question asks for teaspoons per cup
then
you divide the number of teaspoons by the total cups
4: 2/3=6 teaspoons per cup
If the question asks for cups per teaspoon
then
you divide the number of cups by the number of teaspoons
so
2/3:4=2/12=1/6 cups per teaspoonon