The car drove for 2 hours at 78 km / h, the next 3 hours at 84 km / h. On the way back

The car drove for 2 hours at 78 km / h, the next 3 hours at 84 km / h. On the way back, the car spent 4 hours. find the speed of the car on the way back.

1) Find out the path covered by the car in 2 hours, if it is known that its speed was 78 km / h.
78 * 2 = 156 km.
2) Find out the path traveled by the car in the next 3 hours, if it is known that its speed was 84 km / h.
84 * 3 = 252 km.
3) We find out the speed of the car on the way back, if it is known that it took 4 hours on the way back, and the distance that she had to overcome was 252 km and 156 km.
(156 + 252): 4 = 102 km / h.
Let’s compose an expression and find its value.
II.
(78 * 2 + 84 * 3): 4 = 102 km / h.
Answer: the speed of the car on the way back was 102 km / h.