Answer:
2/7
Explanation:First, determine how many washcloths of each type there are.
There are 4 white washcloths.
Since there are twice as many green washcloths as white washcloths, there are 8 green washcloths.
Since there are twice as many red washcloths as green washcloths, there are 16 red washcloths.
So, there are 28 washcloths in all.
Therefore, the probability that Maria picks a green washcloth is 8 out of 28, or , which simplifies to .