how would you construct a truth table for these compound proposition? im so confused
(a) if P then ((notP) and Q)
(b) P and ((not P) and Q)
(c) (not P) or (not Q)
All of those have two variables in them, which means you need $\displaystyle 2^{2}$ rows in the table. In general, if you have $\displaystyle n$ variables, you need $\displaystyle 2^{n}$ rows. I'll start you off on the first one. I tend to build up truth tables from smaller chunks of the expression:
$\displaystyle
\begin{array}{c|c|c|c}
P &Q &\neg P &(\neg P)\land Q\\ \hline
T &T &F &F\\
T &F &F &F\\
F &T &T &T\\
F &F &T &F
\end{array}
$
Do you see how to continue?
Go to this web site and play around with various examples.
Change to just 'p and q'. Then to 'p or q' etc.