Answer:

Step-by-step explanation:
we know that
The area of a circle is equal to

In this problem we have

Substitute and find the area

Remember that
subtends the area of complete circle
so
by proportion
Find the area of the shaded regions
The central angle of the shaded regions is equal to 

Ok so if you follow the process of pemdas is should be easy pemdas equals: parentheses, exponents, multiple and divide from left to right, lastly add and subtract from left to right
3/9 is your answer. 3+6=9 and there are 3 red marbles.