6. A boat can travel 36 mi downstream in 2 hours Coming back upstream, the boat takes 3 hours. What is the rate of the boat in still water? What is the rate of the current?

Step 1 ：1. Let the rate of the boat in still water be \(b\) miles per hour, and the rate of the current be \(c\) miles per hour.

Step 2 ：2. Downstream speed: \(36 = (b + c) * 2\)

Step 3 ：3. Upstream speed: \(36 = (b - c) * 3\)

Step 4 ：4. Solve the equations simultaneously: \(\begin{cases} 2b + 2c = 36 \\ 3b - 3c = 36 \end{cases}\)

Step 5 ：5. Divide the first equation by 2: \(b + c = 18\)

Step 6 ：6. Divide the second equation by 3: \(b - c = 12\)

Step 7 ：7. Add the two equations to eliminate \(c\): \((b + c) + (b - c) = 18 + 12\)

Step 8 ：8. Solve for \(b\): \(2b = 30\) and \(b = 15\)

Step 9 ：9. Plug \(b\) back into one of the equations to find \(c\): \(15 + c = 18\)

Step 10 ：10. Solve for \(c\): \(c = 3\)