Question 1097567
x=gallons of 20% acid
700-x=gallons of 30% acid
the pure acid in each is .20x+.30(700-x)=700*.24
.20x+210-.30x=168
-.10x=-42
x=420 gallons of 20%
700-x=280 gallons of 30%
The concept of pure acid is the per cent * volume
Also
24% is 4/10 of the way from 20 to 30, so 6/10 of the acid should be 20%.  .6*700=420.