Answer:
There are 3 green marbles in the box.
Step-by-step explanation:
15% = 0.15
To figure out how much 15% of 21 is, you must multipl the decimal form of the percentage by the whole number. This will give you how much of that number that percentage is.
0.15 * 21 = 3.15
But you can't have 0.15 of a marble, so you must round as well.
3 green marbles in the box.
