One possible way: -86+(4*12)=-38 -86 is the number where the diver is. 86 feet below the surface. 4*12 is the total number of feet he has ascended in 12 minutes. Because he is ascending, so you add 4*12 (or 48) to -86. The answer is -38, meaning he's 38 feet below the surface.
Take 72 ( 6 foot in inches) subtract 22 1/2 from it. You get 49.5. divide 49.5 by 2 and you get 24.75 on each side of the wall. You're welcome . Dont forget to show work.