The system mx+ny=p has the solution (1,3), where rx+sy=t
m, n,p, r,s and t are non zero real numbers. which of the following system would not have (1,3) as a solution.

Given:

The system Mx+Ny=P has a solution (1,3) where Rx+Sy=T; M, N, P, R,S and T are non-zero real numbers.

Solve for M, N, R, P, S, T:

M +3N = P
R + 3S = T

The given choices should simplify to the equations above. 

A) Mx +Ny = P
     7Rx + 7Sy = 7T
     7(Rx + Sy) = 7T
     Rx + Sy = T
remarks: CORRECT

B) (M+R)x + (N+S)y = P +  T
    Rx + Sy = T
     Mx + Rx + Ny + Sy = P + T
     Mx + Ny + T = P + T
     Mx + Ny = P
remarks: CORRECT

C) Mx + Ny = P
    (2M - R)x + (2N - S)y = P - 2T
    2Mx - Rx + 2Ny - Sy = P - 2T
    2(Mx + Ny) - (Rx + Sy) = P - 2T 
    2P - (Rx + Sy) = P - 2T
remarks: INCORRECT