9. (\frac{7\text{ mi}}{\frac{1}{3}\text{ gal}}=\frac{7divsquare}{squaredivsquare}=\frac{7\timessquare}{square…

Explanation:

Step1: Recall division - fraction rule

When dividing by a fraction $\frac{a}{b}$, it is equivalent to multiplying by its reciprocal. So $\frac{7}{\frac{1}{3}}=7\div\frac{1}{3}$. Here, the first blank in the numerator of the second - fraction is 7 and the first blank in the denominator is 1, and the second blank in the denominator is 3. $7\div\frac{1}{3}=\frac{7\div1}{1\div3}$

Step2: Convert division to multiplication

Since dividing by a fraction $\frac{1}{3}$ is the same as multiplying by its reciprocal 3, we have $7\div\frac{1}{3}=7\times3$. The numerator of the third - fraction is $7\times3$ and the denominator is $1\times1$. $7\times3=\frac{7\times3}{1\times1}$

Step3: Calculate the result

$7\times3 = 21$.

Answer:

$\frac{7\text{ mi}}{\frac{1}{3}\text{ gal}}=\frac{7\div1}{1\div3}=\frac{7\times3}{1\times1}=\frac{21}{1}=21$ miles per gallon. So the blanks should be filled as follows: $\frac{7\text{ mi}}{\frac{1}{3}\text{ gal}}=\frac{7\div1}{1\div3}=\frac{7\times3}{1\times1}=\frac{21}{1}$; 21 miles per gallon. The blanks from left - to - right, top - to - bottom are: 1, 1, 3, 3, 1, 1, 21, 1, 21.