How can you tell if two fractions are equivalent explain

You can find a common denominator. Then you multiply or divide the denominators to equal to the common denominator. Or if you can you can simplify it. Remember, whatever you do to the numerator you have to do to the denominator.
Ex. 4/10 and 2/5
the common denominator is 10. 5*2=10 and 2*2=10 So the fraction is now 4/10.
Now you know the fractions are equivalent

The denominator has to be the same or multiple of the denominator

The probability of picking 2 green markers is 2/10