The coordinates of the fourth vertex are (0,0). I hope this helps!
56.5ft x 17ft x 1ft = 960.5ft^3.
The question wants the answer in ft^3. One of the measurements is given as 13 inches but that converts to 1ft. And with the volume formula for rectangles is widthxlenghtxheight. Plug in the numbers.
So, how much acid is there in 6 gallons? well is 20% acid or (20/100), so the amount of acid in it just (20/100) * 6 or 1.2, the rest is say water.
now, if we want a 90% solution, and say we add "y" gallons, how much acid is in it? well (90/100) * y, or 0.9y.
now let's add "x" gallons of pure acid, now, pure acid is just pure acid, so is 100% acid, how much acid is there in it? (100/100) * x, or 1x or just x.
we know whatever "x" and "y" amounts are, they -> x + 6 = y
and we also know that x + 1.2 = 0.9y
Answer:
A... .................. ....