Your answer for problem 1 looks good. And the idea you used can be applied to the other two problems:
For instance for 2., you would choose 1 blemished apple ( $\left( \begin{array}{c} 8\\\1 \end{array}\right)$ possible ways), and 4 unblemished apples ($\left( \begin{array}{c} 92\\\4 \end{array}\right)$ possible ways).
So the probability of 1 blemished apple (and 4 unblemished) is $$\frac{ \left( \begin{array}{c} 8\\\1 \end{array}\right)\left( \begin{array}{c} 92\\\4 \end{array}\right) }{\left( \begin{array}{c} 100\\\5 \end{array}\right) }$$