Dogs in the GoodDog Obedience School win a blue ribbon for learning how to sit, a green ribbon for learning how to roll over, and a white ribbon for learning how to stay. There are dogs in the school.
62 have blue ribbons, 55 have green ribbons, and 63 have white ribbons.
32 have a blue ribbon and a green ribbon; 31 have a green ribbon and a white ribbon; 38 have a blue ribbon and a white ribbon.
16 have all three ribbons.
How many dogs have not learned any tricks?
Students in the AoPS course Intro to Counting and Probability are expected to complete homework problems but members at web2.0calc do not really care as long as you are learning and not asking as to do your full homework.
This hint will be very beneficial.
draw a venn diagram. It's going to be the most useful thing you are going to use in your current week.
Ask if you don't understand anything.