Math
posted by HELP HELP HELP MNHS .
In the Math department of a school, 10 teachers have YM accounts, 13 have GM accounts, and 6 have both accounts. How many teachers in Department have YM or GM accounts?

4 have YM only
7 have GM only
6 have both
11 have one or the other but not both.
17 have one or the other or both.