How to convert 8.5 hours to hours and minutes

A. 4.25 hrs4 25/100 reduces to 4 1/41/4(60) = 60/4 = 15 minutes
    so 4.25 hrs = 4 hrs and 15 minutes

b. 8.5 hrs8 5/10 reduces to 8 1/21/2(60) = 60/2 = 30 minutes
    so 8.5 hrs = 8 hrs and 30 minutes

c. 6.2 hrs6 2/10 reduces to 6 1/51/5(60) = 60/5 = 12 minutes
    so 6.2 hrs = 6 hrs and 12 minutes

d. 10.8 hrs10 8/10 reduces to 10 4/54/5(60) = 240/5 = 48 minutes
    so 10.8 hrs = 10 hrs and 48 minutes

What class is this? i have no idea and i'm not going to give you the wrong answer. do you have a graph that goes with all the questions