Substitute the n value into the equation. The n repersents the 'nth' term.
K (1) = 2(1) + 3
K = 5
Therefore, when n = 1, K = 5
Same goes t any other term.
K (3) = 2(3) + 3
K = 9
So, when n = 3, K=9
Just keep applying the same rule. Also, make sure that you answer it with a sentence at the end. This should always help you and the marker see that you are confidence with your answer...
I hoped I helped out. Good luck. :)