SAT math problem

<p>of the 40 students in a grade, 19 are taking math 17 are taking french and 18 are taking physics. if every student takes at least 1 of these three classes, how many students are enrolled in exactly 2?</p>

<p>a.11
b. 12
c. 13
d.14
e. cannot be determined. </p>

<p>I said e, but then again I'm bad at math.</p>

<p>what is this type of question called?</p>

<p>its E because u dont know how many are taking all three</p>