Question 1124468
-----
1. edwin is 25 years younger than his father. however, his father will be twice his age in 10 years. find the ages of edwin and his father? 
2. if 5 parts of alcohol is mixed with 20 parts of water, what part of the mixture is alcohol?
3. a chemical engineer mixed 40ml of 35% hydrochloric acid solution with 20ml of 50% hydrochloric acid solution. what is the percentage of the hydrochloric acid of the new solution?
4. how many liters of water must be extracted to 20 liters of 12.5% salt solution to make it 20% salt solution?
-----



1:

{{{system(e=f-25,f+10=2(e+10))}}}
Solve however you want.


2:

{{{5/(5+20)=5/25=1/5}}}