Whats the function rule when inputs 2,3,4,5 and outputs 2,5,8,11?

Answer 1

notice that the difference in your inputs in 1, while the difference in your outputs is 3
so you have a slope of 3

let's start with y = 3x + b
when x = 2, y = 2
so
2 = 3(2) + b
-4 = b

f(x) = 3x - 4

check with a few values.