SOLUTION: whether (~p disjunction (p-->q))-->~q is a tautology without using truth table?

[~p V (p-->q)]--> ~q

A counter-example is when p and q are both true

[~T V (T-->T)]--> ~T

Replace ~T with F in both places:

[F V (T-->T)]--> F

Replace (T-->T) with T

[F V T]--> F

Replace [F V T] with T

T--> F

Replace that with F

F.

So it isn't a tautology.

Edwin