Well what you want to do is sum them all up which would be 36 , then you want to simplfy 36 , since you have 3 diffrent coins you want to divide 36/3 , 12 then you want to simply 12 because its even and can be simplyed ,12/3 , you would get for 4 and he chooses one random at random , your answer would come out to 1/4
