Answer:
9
Step-by-step explanation:
Ans n solution can refer in the picture
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: its b
Step-by-step explanation:
0.5x + 78.2 = 287
-78.2 -78.2
subtract 78.2 on both sides you will then get 0.5x = 208.8 you will then divide by 0.5 and the answer is x = 417.6