Step-by-step explanation:
Let's first calculate how many liters of actual acid we have here. 25% of 36 gives us 0.25×36=9 liters of acid. For the acid to drop to 10% we need to calculate how much liters 100% would be. 100%=10%x (x here is how many 10% fit in 100%, right now that is easy but in case of a more difficult question). We get x=10. So the total is 10 time more liters then the 9 liters of acid we already have, which is 90. now we subtract 9 from that 90 because that is acid and we are left with 81 liters. we started with 0.75×36 liters of water which is 28 so we subtract that from 81 because the question is how much we need to add. This gives us 53 liters.
