If k liters of liquid leak out every x hours, we can compute the amount of liters that leak out every hour:
[tex] x \text{ hours} = k \text{ liters} \implies 1 \text{ hour} = \dfrac{x \text{ hours}}{x} = \dfrac{k}{x} \text{ liters} [/tex]
So, with each passing hour we lose [tex] \frac{k}{x} [/tex] liters. So, in [tex] y [/tex] hours we lose
[tex] y \times \dfrac{k}{x} = \dfrac{ky}{x} [/tex] liters.
Each of this liters costs 6$, so we lose a total of
[tex] 6 \times \dfrac{ky}{x} = \dfrac{6ky}{x} [/tex] dollars.
