the number of passengers is not a multiple of 2, 3 or 5 but it is a multiple of 7
The lowest multiple of 7 that is not a multiple of 2, 3 or 5 is 7
The next multiple after 7 that is not a multiple of 2, 3 or 5 is 49
7 x 1 = 7
7 x 2 = 14 ( can be divided by 2 )
7 x 3 = 21 ( can be divided by 3 )
7 x 4 = 28 ( can be divided by 2 )
7 x 5 = 35 ( can be divided by 5 )
7 x 6 = 42 ( can be divided by 2 )
7 x 7 = 49