Count the tally marks for the "solid" in the middle row. The first portion is a group of 5 as shown by the slash mark. The second portion of that row is one short of five, so it's another 4 tallies. Overall, we have 5+4 = 9 tallies for the "solid".
This is out of 30 spins total. Therefore, we arrive at 9/30 = (3*3)/(3*10) = 3/10