The answer is 13, i got this by using the pythagorean theorem. a^2 + b^2 = c^2. in this case it would be 84^2 + b^2 = 85^2. then that would turn into 7056 + b^2 = 7225, subtract both sides by 7056 to get b^2 = 169, then square 169 to get 13 :)
Because all the coordinates of a line has the same slope. So, we can use any two of them to find the slope.
Tom has 26 marbles. if you need to show your work it would be 13x2= 26 and 26+13=39