Nope. Her solution doesn't seem reasonable. In order to subtract 9/12 from 10 7/12 you must convert 10 7/12 to an improper fraction. You should then have 127/12 where she has 10/12.
I think it's because all the other colors are dark and the darker the color, the more heat it absorbs. yellow or white or basically light colors would reflect the light. this is just if it is talking in terms of temperature.