Posted by james on Tuesday, December 8, 2009 at 8:37am.
When Professor Sum was asked by Mr. Little how many students were in his classes, he answered, “All of them study either languages, physics, or not at all. Onehalf of them study languages only, onefourth of them study French, oneseventh of them study physics only, and 20 do not study at all.” How many students does Professor Sum have?

math  PsyDAG, Tuesday, December 8, 2009 at 10:15am
1/2 + 1/4 + 1/7 = X  20
Solve for X.
I hope this helps.