It would look like this: O=C=O
Hope this helps you out.
34 less than (-34) the product of (multiply) 14 (14) and an unknown (x) is (=) 78 (78)
-34+14 times x=78
14 times x=14x
14x-34=78
add 34 to both sides
14x=112
divide both sdies by 14
x=8
the number is 8
180-50=130
x-y=130
x+y=50
2x=180
x=90
90+y=50
y=50-90
y=-40
Since its out of 15 marbles all together and all you need to find is the probability of 3 blue marbles you would have to divide 3 by 15. The outcome would be 0.2 or in your case... B. - 0.20