Can someone me with this and show your work

20% of 50 = 50 * (20/100) = 50 * (1/5) = 10

First, you multiply 50 by .20 to get 10. 10 is your answer. The tricky thing is when you are using %s to divide you multiply and to multiply you divide.
This is the work
50 x .20 = 10 blue marbles