200 g of salt was added to a 10% salt solution and a 30% solution was obtained. Find the mass of the original solution.

Let us denote by x the mass of the initial solution, expressed in grams.

According to the condition of the problem, the concentration of the initial solution was 10%, therefore, the initial solution contained (10/100) * x = 0.1x g of salt.

In the wording of the condition for this task, it is reported that after 200 g of salt was added to this solution, the result was a 30% solution, therefore, we can draw up the following equation:

(0.1x + 200) / (x + 200) = 30/100,

solving which, we get:

(0.1x + 200) / (x + 200) = 0.3;

0.1x + 200 = 0.3 * (x + 200);

0.1x + 200 = 0.3x + 60;

0.3x – 0.1x = 200 – 60;

0.2x = 140;

x = 140 / 0.2 = 700 g.

Answer: 700 g.