The boat sailed 2 hours along the river, and then 1 hour along the lake and sailed 54 km in total

The boat sailed 2 hours along the river, and then 1 hour along the lake and sailed 54 km in total. What is the boat’s own speed if the speed of the river is 1.5 km / h?

1) Let x km / h be the boat’s own speed (speed in still water).

2) Then (x + 1.5) km / h is the speed of the boat when moving along the river.

3) ((x + 1.5) * 2) km the boat passed along the river in 2 hours, (x * 1) km it sailed along the lake.

4) (2 * (x + 1.5) + x) km the boat passed all along the river and lake.

5) According to the condition of the problem, the boat covered 54 km in total, so we make up the equality:

2 * (x + 1.5) + x = 54.

6) Let’s solve the equation:

2x + 3 + x = 54;

3x = 54 – 3;

3x = 51;

x = 51: 3;

x = 17.

7) x = 17 km / h – own speed of the boat.

Answer: 17 km / h.