A bus travels at a certain average speed for a distance of 75 km and then travels a distance of 90 km at an average speed of 10 km//hr more than the first speed. If it takes 3 hours to complete the total journey, find its original speed.

Explanation

To solve the problem, we need to find the original speed of the bus. Let's denote the original speed of the bus as \( x \) km/hr.

### Step 1: Set up the equations for time taken
1. The bus travels 75 km at a speed of \( x \) km/hr.
- Time taken for this part of the journey = \( \frac{75}{x} \) hours.

2. The bus then travels 90 km at a speed of \( x + 10 \) km/hr.
- Time taken for this part of the journey = \( \frac{90}{x + 10} \) hours.
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