Answer:
13. 23 boat rides; 22 are full, and the first one has 301 passengers.
12. $11,067.50
So, I came up with something like this. I didn't find the final equation algebraically, but simply "figured it out". And I'm not sure how much "correct" this solution is, but it seems to work.
To find the superficial area of a prism you have to do base perimeter * height
So find the perimeter of the right triangle: 9+8+5 = 22 yd
Then find the superficial area 22*12 = 264 yd^2