I am trying to prove that the problem of having a person at the minimum x number of intersections to be able to see each street is NP-Complete. I think that the street problem is very similar to the Vertex Set problem, and to prove it is NP-Complete I could some form of reduction like 3-SAT to Vertex Set but with my problem in place, to verify the requirement that it is NP-Hard (I can prove it is NP). I'm having an extreme amount of trouble getting started with this however. I've looked many examples of reduction but cannot think how to start my own. How would I show the reduction from 3-SAT to the street problem/Vertex Set?