| Solution 1 | Solution 2 | Mixture | |
| Nitric Acid | 20% | 70% | 40% |
| Others | 80% | 30% | 60% |
| x | y | F |
\(x+y=F\)
\(y = F-x\)
\(0.2x+ 0.7y = 0.4 F\)
\(0.2x+ 0.7(F-x) = 0.4 F\)
\(0.2x +0.7F-0.7x = 0.4F\)
\(0.5 x = 0.3F\)
\(x = 0.6F\)
\(y = 0.4F\)
60% should be taken from the 20% solution and 40% from the other solution.