Find the distance between those points
diameter/2=radius
distance betwen (x1,y1) and (x2,y2) is

given
(3,7) and (7,3)




D=4√2
diameter/2=(4√2)/2=2√2
radius is 2√2
In short, to convert two fractions to have the same denominator, we simply multiply one by the denominator of the other, so in this case, we'll multiply 1/3 by 5, top and bottom, and 1/5 by 3, top and bottom, thus
![\bf a^{\frac{ n}{ m}} \implies \sqrt[ m]{a^ n} \qquad \qquad \sqrt[ m]{a^ n}\implies a^{\frac{ n}{ m}}\\\\ -------------------------------](https://tex.z-dn.net/?f=%5Cbf%20a%5E%7B%5Cfrac%7B%20n%7D%7B%20m%7D%7D%20%5Cimplies%20%20%5Csqrt%5B%20m%5D%7Ba%5E%20n%7D%20%0A%5Cqquad%20%5Cqquad%0A%5Csqrt%5B%20m%5D%7Ba%5E%20n%7D%5Cimplies%20a%5E%7B%5Cfrac%7B%20n%7D%7B%20m%7D%7D%5C%5C%5C%5C%0A-------------------------------)
The number is most likely 15 because if you one recorded 3 baseball cards and 9 baseball cards it would be most reasonable to have it be 15