6. Practice similar
If a boat travels from Town A to Town B, it has to travel $198 \mathrm{mi}$ along a river.
A boat traveled from Town A to Town B along the river's current with its engine running at full speed. This trip took $11 \mathrm{hr}$.
Then the boat traveled back from Town B to Town A, again with the engine at full speed, but this time against the river's current. This trip took $16.5 \mathrm{hr}$.
Write and solve a system of equations to answer the following questions.
The boat's speed in still water with the engine running at full speed is
The river current's speed was
Use mi for miles, and hr for hours.

Step 1 ：Let's denote the speed of the boat in still water as 'b' and the speed of the river current as 'r'.

Step 2 ：When the boat travels from Town A to Town B along the river's current, the effective speed of the boat is (b + r). Given that the distance is 198 miles and the time taken is 11 hours, we can write the equation as: \((b + r) * 11 = 198\).

Step 3 ：When the boat travels back from Town B to Town A against the river's current, the effective speed of the boat is (b - r). Given that the distance is 198 miles and the time taken is 16.5 hours, we can write the equation as: \((b - r) * 16.5 = 198\).

Step 4 ：Solving this system of equations, we find that 'b' equals 15 and 'r' equals 3.

Step 5 ：Final Answer: The boat's speed in still water with the engine running at full speed is \(\boxed{15 \, \text{mi/hr}}\) and the river current's speed was \(\boxed{3 \, \text{mi/hr}}\).