Speed of the boat in still water 11.9 km / h. , and along the river – 14.7 km / h. Find the speed of the river.

Brief notation of the problem condition:
ϑ boats ̶ 11.9 km / h;
ϑ on tech. ̶ 14.7 km / h;
ϑ current ̶?
Decision:
The speed of a boat moving along the river is equal to the sum of the speed of the boat in still water and the speed of the river, which can be written as a formula:
ϑ on tech. = ϑ boats + ϑ tech.;
From the formula it follows that:
ϑ current = ϑ in flow – ϑ boats;
ϑ current = 14.7 – 11.9 = 2.8 (km / h);
Answer: 2.8 km / h.