A is the greatest number and C is the least number.
Answer:
3 gallons
Step-by-step explanation:
Let
x ----> the amount of pure acid (100% solution) in gallons
Remember that



we know that

solve for x


therefore
3 gallons of pure acid should be mixed with 3 gallons of a 20% acid solution in order to get a 60% acid solution
I believe it coukd be utself or abother answer by itself times x