Use a Venn diagram.
There are 3 in the intersection of all three circles.
Work your way from inside out.
I have a problem that I have absolutely no idea how to approach.
At a high school science fair, 34 students received awards for projects, 14 awards for biology projects, 13 for chemistry projects, 21 for physics projects, and 3 students got awards in all three subjects. How many students received awards for exactly one subject matter?
Any help would be appreciated, thanks.