Answer:
How many miles does he ride his bike there and back?
6 miles.
What information is extra?
The hour at which he leaves his house.
Explanation:
We know that he rides 3 miles each way.
Then he rides 3 miles from his house to his friend's house, and another 3 miles from his friend's house to his house.
So he rides 3 miles both times, if we add that, we get:
3 miles + 3 miles = 6 miles
So:
How many miles does he ride his bike there and back?
6 miles.
And to answer the other question, we need to look at the given information that we did not use in this calculation. In this case, is the hour at which he leaves his house.
Notice that we never did use the fact that he leaves his house at 4 p.m.
Then:
What information is extra?
The hour at which he leaves his house.