The letters L, M, N, O, P, Q, R, S and T in  their order are substituted by nine intergers 1 to 9 but not in that order. 4 is assigned to P. The difference between P and T is 5. The difference between N and T is 3. What is the integer assigned to N ?

Answer: C. 6

P = 4 and T - P = 5 → T = 9.
T - N = 3 and T = 9 → N = 6.