Joint variation means that w=kxy where k is constant.
Finding k:
12=k*2*18
12=36k
k=1/3
Now plug in second set of values
16= 1/3*6*y
16=2*y
y=8
Final answer: 8
The first thing that you have to do is line it up from least to greatest: 98,104,104,105,111,117,120,121. Then you add all of the numbers and divide the total of all the number of scores she has. 880/8=110. 110 is the answer of your question. ( I got 8 because I had to count all the numbers and I got 880 because I added all the numbers).
Your guesses are correct.
I believe it is 4/12 since you have a total of 12 marbles and only 4 are red plastic ones