lf P(n) is a statement such that P(3) is true. Assuming P(k) is true is true for all then P(n) is true
Since, P(3) is true.
Assume P(k) is true P(k + 1) is true means, if P(3) is true P(4) is true P(5) is true and so on..
So statement is true for all n 3.