Solution

Water | \(96%\) | - | \(100\%\) | \(95\%\) |

Salt | \(4%\) | - | \(0\%\) | \(5\%\) |

-- | \(100\text{kg}\) | - | \(x\) | \(100-x\) |

\(0.96(100) - x = 0.95 (100-x)\)

\(x= 20 \text{kg}\)

Since there are 96 kg water and 20 kg evaporated water, thus the percentage of the evaporated water is \(\frac{20}{96} (100) = 20.83\%\)