Question

How many quarts equals five gallons, and how many liters equals five gallons ?

Answer 1

The name 'quartz' sounds like quarter $\to \frac{1}{4}$
From this you can see the link between $4$ quarts = $1$ gallon.
Solving for quarts in $5$ gallons
Showing every steps:
Using ratios $\frac{\text{quarts}}{\text{gallons}}\to \frac{4\text{quarts}}{1\text{gallon}}$
But we need $5$ gallons.
Then $\frac{4}{1}=\frac{\text{quarts count}}{5}$
Multiply both sides by $5$
$\frac{4}{1}\times 5=\frac{\text{quarts count}}{5}\times 5$
Write as $4\times 5$ = quarts count $\times \frac{5}{5}$
But $\frac{5}{5}=1$
$4\times 5=$ quarts count $\times 1$
$20$ = quarts count
So $20$ quarts make $5$ gallons.
Solving for litres in $5$ US Gallons
Not showing every step
Understood that $3.785411784$ litres = $1$ US Gallon
Use litre conversion as $3.785$

As a ratio
$\frac{3.785\text{litres}}{1\text{US gallon}}=\frac{\text{litres count}}{5}$
litres count $\approx 5\left(3.785\right)\approx 18.925$ litres $\sim \sim 5$ US gallons