When encountering questions about speed, time and distance and you are unsure about the formula.
Draw out the DST triangle like the one above.
If you are looking for Distance, cover D with your finger and the formula would be Speed x Time.
If you are looking for Speed, cover S with your finger and the formula will be Distance over Time.
If you are looking for Time, cover t with your finger and the formula will be Distance over Speed.

Let’s look at the first question. They are looking for the average speed of the journey.
The formula is Distance over Time. We have our time which is 2hours but we do not have our Distance. So we got to work out using the 2 speed and time given to us.

2nd question is similar. We are looking for time but do not have the distance.
So we take the information of speed and time given to us from jogging towards the park to find the distance between his house and the park.