Idk about number 4 but I think the other ones are correct
X represents the amount of children's tickets
y represents the amount of adult's tickets
8(x+y) = 54
An arithmetic sequence (a_n) is as follows:

where

is the first term and d is the constant difference,
thus, we see that the n'th term of an arithmetic sequence is

in our particular case d=5, the third term is 8, so we have:

and the general term is

,
Answer: first term is -2, n'th term is -2+5(n-1)
(100)= 0.25*100=15 times.
<span>SO, the train will be late 15 times in 100 days.
Hope i helped:P </span>