comingsoon,

distance to minnies house = 5 miles they walked "the remaining mile"
Look close, it doesn't say "the remaining distance" or "the remaining miles" it says "the remaining MILE" which means there is only one mile left to walk.

so total distance = 5 miles + 1 mile(the remaining mile) = 6 miles

If you are wondering how the total time is 3/4 hours, 3/4 hours = 45 mins

If you are wondering how the speed of the bike is 12, its because it takes him half an hour to travel 6 miles, 6/(1/2) is 12

If you are wondering how time taken to go to minnies house is 5/12, its because 
                                time = distance to minnies house/speed  of bike= 5/12

I hope you are not wondering anything else.

Cheers