For question 23, remember that the Factor Theorem tells you that if $a$ is a solution of $P(x) = 0$, then $(x-a)$ is a factor of $P(x)$.

Question 25 is telling you the values you would get by plugging in $1$ and $2$ in the polynomial. That information should help you find what $a$ and $b$ should be.

For question 29 it is important to remember that we can treat rational expressions in a similar way we do regular fractions. Try factoring the denominators to simplify the expression.