Chapter 6.4, Problem 13P

a. By rewriting the division problem
   $\frac{18}{33}÷\frac{9}{11}=?$
as a multiplication problem with an unknown factor, explain why it is valid to divide the fractions as follows:
   $\frac{18}{33}÷\frac{9}{11}=\frac{18÷9}{33÷11}=\frac{2}{3}$
b. Give an example of a numerical fraction division problem that can be made easy to solve by using the method of dividing the numerators and dividing the denominators that is demonstrated in part (a).