For how many values of k does the following system of equations have at-least one solution?
x+y=1; kx+y=3; x+ky=5;
Adding the second and third equations we get (k+1)(x+y)=8, and hence k+1=8.
Thus , k=7. The valus of x=1/3, y=2/3 satisfy the equations if k=7. Hence the answer is B.