Prove by induction or strong induction that every even integer greater than 30 can be written in the form:

So I started off with my basis step this way:

So the basis step is true.

Then follows the inductive step:

Then I realise I am stuck here. I don't know how I should move on from here. The usual inductions are like I could find something that looks like the basis step and then replace the k+1 part with the basis claim. But I can't do this in this one.

Thanks for any help.