To a solution weighing 90 g, containing 3% solute, 110 g of a 10% solution was added.

To a solution weighing 90 g, containing 3% solute, 110 g of a 10% solution was added. Calculate the mass of water in the new solution.

We calculate the mass of the solute in the first solution: 90 * 3/100 = 2.7 g.
We do the same with the second solution: 110 * 10/100 = 11g.
Find the mass of the solute in the resulting solution. To do this, add the masses of the solutes of the first and second solutions: 2.7 + 11 = 13.7 g.
We find the mass of the entire solution after draining. To do this, add the masses of the first and second solutions: 90 + 110 = 200g.
It turns out that in a solution (weighing 200 g) 13.7 g is the mass of the solute. The rest is a mass of water. This means that the mass of water is: 200 – 13.7 = 186.3 g – the answer.