Addison, Amanda, and Ashley can paint a room together in 6 hours. If Addison and Amanda could do it in 10 hours, how many hours would it take Ashley by herself?
+36916 1/Ashley + 1/amanda + 1/ addison = 1/6
1/addison + 1/amanda = 1/10
1/10 + 1/ashley = 1/6
1/ashley = 2/30
ashley = 30/2 = 15 hours
