Can someone help me solve the question 151617 PLS PLSSoluti

Can someone help me solve the question 15,16&17 ! PLS PLS!

15.

There are 6C4 = 15 sets of majors.

16.

There are 2 ways to choose A or F.

Then the next 3 will be chosen from the reaming 4 majors. There are 4C3 = 8 ways to do that.

Hence, there are 2*4 = 8 wways to do this. [answer]

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17.

We set I and S to be there.

Hence, the two other memebers must choose from the 4 other subjects.

Hence, there are 4C2 = 6 ways to do that. [ANSWER, 6]