| S1 | S2 | S3 | Mixture | |
| Silver | 20% | 100% | 0 | 25% |
| Lead | 30% | 0 | 100% | \(33\frac{1}{3}\%\) |
| Total | 100 | x | y | 100+x+y |
\(0.2(100) + x +0y = 0.25 (100+x+y)\)
\(20+x = 25 +0.25x +0.25y\)
\(0.75x = 5+ 0.25y\)
\(x = \frac{20}{3}+ \frac{y}{3}\)
\(0.3(100) + 0x +y = \frac{1}{3} (100+x+y)\)
\(30 + y = \frac{100}{3} + \frac{x}{3} + \frac{y}{3}\)
\(-\frac{10}{3} +\frac{2y}{3} = \frac{x}{3} \)
\(x = -10+2y \)
\(\frac{20}{3}+ \frac{y}{3} = -10+2y\)
\(\frac{50}{3}= \frac{5y}{3}\)
\(y = 10\)
\(x = 10\)
To obtain the mixture a 10 lbs silver and a 10 lbs lead are needed.