In a group of 72 students, each student is registered for at least one of three classes – History, Math and English. Twenty-five students are registered for History, twenty-five students are registered for Math, and thirty-four students are registered for English. If only three students are registered for all three classes, how many students are registered for exactly two classes? Choose one: A) 13 B) 10 C) 9 D) 8 E) 6
A U B U C = A + B + C - AB-BC-AC + ABC   72 = 25 + 25+ 34 -AB-BC-AC +3 =&gt; AB+BC+AC = 15   6xactly Two classes = AB+BC+AC - 3ABC = 15 -3*3= 
<gadget id="calculator">15 -3*3</gadget>
<output>6</output>
6   Hence 6
<result>E</result>
In a group of 72 students, each student is registered for at least one of three classes – History, Math and English. Twenty-five students are registered for History, twenty-five students are registered for Math, and thirty-four students are registered for English. If only three students are registered for all three classes, how many students are registered for exactly two classes?