Total time is 39 minutes or 0.65 hours.
Let x be the regular expected time if he would have used his regular speed for the whole trip.
SPEEDS TIMES DISTANCE
regular speed 5 x 5x
running 12 0.65-x 12(0.65-x)
total 0.65 5
Just study and understand the setup, and solve the equation. You can then answer your two questions.