We have 3/24 = r/52
We can simplify 3/24 to 1/8
Now we have 1/8 = r/52
We can multiply both sides by 52 and we get
52 * (1/8) = 52 * (r/52)
(52 * 1)/8 = (52 * r)/52
The (52 * 1)/8 becomes 52/8 and (52 * r)/52 becomes r because the 52's cancel out.
52/8 = r
6.5 = r