The answer would be 6x(5x-2).
Since both terms have x in them, x will be apart of your answer.
The GCF of 12 and 30 is 6.
So you can factor out 6x from both terms.
Hope this helps!
There are a lot of numbers you can think of, for example, 1030, or even 9939, but I don't recommend you put that ;)
Becouse k and n are 'neighbours' so their sum are 180
so k=180-42=138