744/1000 would be your answer
Jon has y stickers and uses 20
jon=y-20
the sisters share y-20 between 2 of them
therefore each sister receives
(y-20) divided by 2 -- (y-20)/2
We take 2 marbles from 20 marbles and the total ways is 20x19:2=190
But we need only 2 red marbles and the ways is 14x13:2=91
And finally we do the division 91:190=91/190 is the probability we need
X = 12
Use the Pythagorean Theorem.
13^2 = 5^2 + x^2
169 = 25 + x^2
Subtract 25 from both sides.
144 = x^2
Take the square root.
12 = x
