Hakeen has 100 plans he want to plant them in row of 8 how many full rows

Divide 100 by 8: 100/8=12.5. 12 full rows and 1 half row so the answer is 12 :)

12 rows and 1/2 because you divide 100 by 8 and it equals 12.5

So first add all of the marbles together: 3+2+6+9=20
Because there are 20 marbles together, that would be your denominator. 
All of the other numbers would be your numerator. So you would have:

3/20 green marbles
2/20 yellow marbles
6/20 blue marbles
9/20 red marbles

So your answer would be the probability of picking a red marble from the bag is 9/20 or 45%