After resting they decided to go for a swim. The depth of the water is 15 times Dean's height. Dean is 4 feet taller than Ron. If Ron stands at 13 feet how deep was the water?
Let's denote the depth of the water by $d$. The depth of the water is equal to the height of the container $h$ minus the height of the object $x$:
$$d = h - x$$
The volume of the water $V$ is equal to the product of the water's depth $d$, the length of the container $l$ and its width $w$:
$$V = d\cdot l \cdot w$$
We know that the product of two numbers is equal to the product of their reciprocals. Thus, we can write:
$$V = \frac{l\cdot w}{h-x}$$
We know that the volume of the water is equal to the product of its width $w$ and its height $y$. Thus, we can write:
$$V = w\cdot y$$
From the last two equations we obtain:
$$\frac{l\cdot w}{h-x} = w\cdot y$$
After cancelling out $w$ from both sides of the equation we get:
$$\frac{l}{h-x} = y$$
We know that the height of the object $