To solve this problem, we need to model the situation using equations for the times taken by the boat both upstream and downstream.

Let's assume:

• $d$ represents the distance the boat is traveling (same distance both upstream and downstream),
• $x$ represents the boat's speed in still water (miles per hour),
• $t_u$ is the time it takes to travel upstream,
• $t_d$ is the time it takes to travel downstream.

Upstream Scenario

When traveling upstream, the boat's effective speed is reduced by the current, which decreases the boat's speed by 10 miles per hour. The boat also takes 3 hours longer than it would in still water.

The effective speed upstream is $x - 10$ miles per hour, and the time it takes to travel upstream can be written as: $t_u = \frac{d}{x - 10} + 3$ (3 hours longer than in still water).

Downstream Scenario

When traveling downstream, the current increases the boat's speed by 8 miles per hour, but the boat takes 5 hours longer than if it were in still water.

The effective speed downstream is $x + 8$ miles per hour, and the time it takes to travel downstream can be written as: $t_d = \frac{d}{x + 8} + 5$ (5 hours longer than in still water).

Total Time

Let $y$ represent the total time it takes to travel both upstream and downstream: $y = t_u + t_d$ Substituting the expressions for $t_u$ and $t_d$: $y = \left( \frac{d}{x - 10} + 3 \right) + \left( \frac{d}{x + 8} + 5 \right)$ Simplifying: $y = \frac{d}{x - 10} + \frac{d}{x + 8} + 8$ This equation gives the total time $y$ as a function of the boat's speed $x$ in still water and the distance $d$.

Coordinate Point $(x, y)$

The equation $y = \frac{d}{x - 10} + \frac{d}{x + 8} + 8$ represents the relationship between the boat's speed $x$ and the total time $y$. To find a specific point $(x, y)$, you need to know the distance $d$ and either the speed $x$ or the total time $y$.

Do you have any specific values for $d$ or $x$, or would you like to proceed with a general solution?

Further questions to expand on this:

1. How does the speed of the current affect the overall travel time upstream and downstream?
2. What would happen to the total time if the current were stronger (e.g., the current speed increased)?
3. How can we find the boat's speed in still water if we only know the total travel time?
4. What would the graph of $y = \frac{d}{x - 10} + \frac{d}{x + 8} + 8$ look like for different values of $d$?
5. Can this model be used for boats on other types of water, like oceans with tides?

Tip: When working with rates and times, always ensure that units are consistent (e.g., hours, miles per hour) to avoid confusion.