Answer:
10 quarts.
Step-by-step explanation:
Work with amounts of pure acid.
There is 0.10*3 quarts of pure acid in the 10% solution.
3*0.10 + 0.75x = 0.60(x + 3) where x is the number of quarts of 75% acid.
0.30 + 0.75x = 0.60x + 1.8
0.15x = 1.5
x = 10 .
