Let's denote the unknown constant speed as "x" km/h.
In the first part of the journey, the car travels for 2 hours at a constant speed. The distance covered in this part is given by the formula: Distance = Speed × Time. Thus, the distance covered in the first part is 2x km.
In the second part of the journey, the car travels for 3 hours at a speed 4 km/h faster than the previous speed. Therefore, the speed in this part is (x + 4) km/h, and the distance covered is (x + 4) × 3 km.
In the third part of the journey, the car travels for 4 hours at a speed 10 km/h slower than the previous speed. Therefore, the speed in this part is (x - 10) km/h, and the distance covered is (x - 10) × 4 km.
The total distance covered is given as 602 km. We can set up an equation based on the distances covered in each part:
2x + 3(x + 4) + 4(x - 10) = 602
Simplifying the equation:
2x + 3x + 12 + 4x - 40 = 602
9x - 28 = 602
9x = 602 + 28
9x = 630
x = 630 / 9
x = 70
Therefore, the first speed of the car is 70 km/h.