In a flask 100 g of 10% hydrochloric acid. How many g in 25% of the same solution of the same

In a flask 100 g of 10% hydrochloric acid. How many g in 25% of the same solution of the same acid must be poured so that after stirring, a 15% solution is formed in the flask.

In the first flask:
100 g – solution
10% – concentration,
0.1 * 100 = 10 g – pure substance.
In the second flask:
x g – solution,
25% – concentration,
0.25x g – pure substance.
After stirring, a solution was obtained in the third flask:
100 + x g. – solution,
15% – concentration,
0.15 (100 + x) g – pure substance.
The pure substance in the third flask is the sum of the pure substance from the first and second flasks. Let’s make the equation:
0.15 (100 + x) = 10 + 0.25x,
15 + 0.15x = 10 + 0.25x,
15-10 = 0.25x-0.15x,
5 = 0.1x,
0.1x = 5,
x = 5: 0.1,
x = 50.
So, the second solution should be 50 g.
Answer: 50 g.