1) Without any restrictions, there are 18*17*16 = 4896 ways that three people can be seated. Then, we have to subtract the cases where they are adjacent.
Case 1: Where all three people are next to each other in a "boomerang" shape. There are 18 ways to choose three consecutive seats. There are then 3! = 6 ways to place those three people, which gives us 18*6=108 possible seatings where they are next to each other.
Case 2: There are two people sitting next to each other, and the third person is not next to either of them (loner, like me).
There are 18 ways to choose two consecutive seats for the two people. There are then 14 ways to choose the third seat for the loner. After the three seats have been chosen, there are 3!=6 ways to place the three people, which gives us 18*14*6=1512 possible seatings.
Subtracting all of them: 4896-1512-108=3276 ways.
Hope this is right!
2) Can't help you since there is a typo. "After steps". No number.