In this situation you FOIL the two equations. Its complex to explain it over text so you should watch a video on how to do it (if you dont know how already)
Multiply K by 3K to get 3K^2 (^2 means squared) Multiply K by -6 to get -6K Multiply 4 by 3K to get 12K Multiply 3 by -6 to get -18 Combine like terms and the final answer is: 3K^2+6K-18