First, identify how many blue marbles there are (5). That's what the numerator (the top number on the fraction) is going to be. From there, take all the numbers given (5, 2, 6, and 5) and add them up (18). This is what you're goign to put as the denominator (the number on the bottom). Lastly, go and make sure that it can't be simplified at all (find the least common factor of the two if there is one.)
