Check the picture below.
now, to get how much is the area of the tiled section, we simply get the area of the whole pool, 53x26, which includes the tiles, and then subtract the area without the tile, the rectangle in the middle, and what's leftover, is the area of the tiled area.

Divide 8.5 by .3 and get 28.3333. She can't make tacos with the extra .3 pounds so the answer is 28 tacos
You solve this by using google.com or YouTube.com
Or just pay attention in class to get this.
T=PV/Rn you just divide both sides by Rn