The boat covered 12 km along the river and 4 km against the current, spending 2 hours

The boat covered 12 km along the river and 4 km against the current, spending 2 hours for the entire journey. What is the boat’s own speed if the current speed is 4 km / h?

Decision:
To solve this problem, we introduce a conditional variable “X”, through which we denote the boat’s own speed. Then, applying the speed formula and based on the data of the problem, we will compose the following equation: 12 / (X + 4) + 4 / (X – 4) = 2. Solving this equation, we obtain 12 (X – 4) + 4 (X + 4 ) = 2 (X ^ 2 – 16) or 12X – 48 + 4X + 16 = 2X ^ 2 – 32 or 16X = 2X ^ 2 or X = 8 kilometers per hour.
Answer: the boat’s own speed is 8 kilometers per hour.