To solve the ratio table, let's first observe the given ratios:

$\frac{54}{63}, \frac{72}{84}, \frac{78}{91}$

We can reduce these ratios to their simplest forms:

1. $\frac{54}{63}$ simplifies by dividing both the numerator and denominator by 9: $\frac{54}{63} = \frac{6}{7}$

2. $\frac{72}{84}$ simplifies by dividing both the numerator and denominator by 12: $\frac{72}{84} = \frac{6}{7}$

3. $\frac{78}{91}$ simplifies by dividing both the numerator and denominator by 13: $\frac{78}{91} = \frac{6}{7}$

All these simplified ratios are equal to $\frac{6}{7}$, which means that the constant ratio is $\frac{6}{7}$.

Now, to find the missing values:

1. In the first row, we know that the ratio is also $\frac{6}{7}$, so if the second column is 7, the corresponding first column value must be 6: $\frac{\text{Missing value}}{7} = \frac{6}{7} \implies \text{Missing value} = 6$

2. In the second row, where the second column is 14, we can similarly apply the same ratio: $\frac{\text{Missing value}}{14} = \frac{6}{7} \implies \text{Missing value} = 12$

So, the completed table is: