I say 90 because 24 is just a little higher than 1/4 of 80 and since 1/4 of 300 is 75, 90 is the best estimate based off the sample survey. Hope this helps!
2 * 7 = 14 (the number of tiles for each row) 23 - 14 = 9 (the number of tiles subtracted from how many tiles that are taken away) 9 tiles are in the seventh row.