Answer:
10.5 liters
Explanation:
In this question you are mixing 6liters of 45% acid solution to get a an acid solution of 80%.
This can be written as;
(0.45 * 6) + (1.00 *x) =0.80 (6+x)
2.7 + x = 4.8 + 0.80x
x-0.80x=4.8-2.7
0.20x=2.1
x=2.1/0.20 =10.5 liters