## To find the final concentration of the mixed solution, you need to calculate the total grams of the solute and the total volume of the solution.

First, let's calculate the total grams of the solute:

- For the 20% sol, you have 50 ml of solution, which means you have 0.2 * 50 = 10 grams of solute.

- For the 15% sol, you have 150 ml of solution, so you have 0.15 * 150 = 22.5 grams of solute.

- For the 35% sol, you have 200 ml of solution, which gives you 0.35 * 200 = 70 grams of solute.

Now, let's calculate the total volume of the solution:

You have 50 ml + 150 ml + 200 ml = 400 ml of the solution in total.

To find the final % concentration of the mixed solution, you divide the total grams of the solute by the total volume of the solution:

Final concentration = (10 + 22.5 + 70) grams / 400 ml

To find the total grams of the solute in the final solution, you can just add the total grams of the solute that we calculated earlier:

Total grams of solute = 10 grams + 22.5 grams + 70 grams

Please note that for more accurate calculations, you would need to consider the density of each solution, as solvents and solutes can have different densities.