What do you want to find?
I'm sorry to tell that if you are trying to get a specific value for k, you can not since there are three variables and two equations!
However, if you are trying to express k in terms of X, that's great!
k = 3p, so 18p is 6k. Sub that into the first equation to get 10k = 1/4X, and from that you can complete the rest.