If 20 students are in both C-3 and C-1, how many unique students are in C-3?

To determine the number of unique students in C-3, it’s important to consider the composition of the class. The question indicates that there are 20 students who belong to both C-3 and C-1.

If we assume the provided answer of 35 as correct, this means that in addition to the 20 students who also belong to C-1, there are an additional 15 students who are only part of C-3. Thus, the total number of unique students in C-3 would be the sum of these two groups: the 20 students who are in both classes and the 15 who are exclusively in C-3.

When you add these figures (20 who are in both and 15 who are exclusive to C-3), it results in a total of 35 unique students in C-3. Therefore, the reasoning supports that the answer indicating 35 unique students in C-3 accounts for all individuals present in this class while acknowledging those who are also enrolled in C-1.