1.) The sum of the digits of a three digit number is 15. If the tenths digit are interchanged, the number is increased by 360. If the units digit is 1/4 of the sum of the hundreds and tens digits, what is the number?

2.) A 90% acid solution is diluted w/ H2O to make a solution 60% acid. When 3 gal. of H2O is added to dilute it again, the solution becomes 40% acid. How much H2O was added to the solution on the 1st instance? How much 90% acid was available at the start?

These are some of the problems that our teacher gave us to study for our quiz that I cannot solve...help pls.