X=25 ...... ................
The answer is 24 because 8 times 3 is 24
18 choose 7
=C(18,7)
=18!/(7!(18-7)!)
=31824
OR
18 choices for first passenger,
17 choices for second passenger,
....
12 choices for 7th passenger,
so total = 18*17*16...12
but there are 7! ways to order the 7 passengers, so
number of groups
=18*17*16...12/7!
=31824 as well
5^12/5^6 Is the correct response. When equal numbers with different exponents are divided then the you must subtract the exponents.
Thus 12-6 = 6.