The only way to get a sum of 6 from the numbers {1,2,3,4} is if v and w are not from this set, or if the question is flawed. Assuming the numbers are 1,2,3,4, this condition is impossible. If we assume the numbers are 1,2,3, and r,s,t,u,v,w,x,y,z are variables in a Sudoku-like puzzle, we cannot solve without the grid. Given the provided answer is 3, there must be missing context or a flaw in the question.