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.
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