The third one down, I think!!!!
Answer:
4 students
Step-by-step explanation:
The total number of students is given by:

Where N is the total number of students, A is the number of students that have taken Math 2A, B is the number of students that have taken Math 2B, and C is the number of students that have taken Math 2C:

4 students in Group A have taken all three classes.
*The number of students that have taken two classes has be subtracted so those students do not get counted twice
Answer: Addition Property of Equality
We add 7 to both sides to go from 19 = 2x-7 to 26 = 2x
The volume would be, 24.
:)