There are two vessels with a salt solution, and in the second vessel there is 2 liters more solution

There are two vessels with a salt solution, and in the second vessel there is 2 liters more solution than in the first one. in the first vessel, the salt content in the solution is 20%, and in the second -50%. Solutions from two vessels were poured into one. The salt content in the new solution was 40%. Determine the amount of solution that was in the second vessel.

Let’s designate the amount of solution in the first vessel through X;
In the second vessel, the amount of solution is X + 2;
The salt content in the first vessel is X * 20% / 100% = 0.2 * X;
Salt content in the second vessel: (X + 2) * 50% / 100% = (X + 2) / 2 = 0.5 * X + 1;
After the solutions were poured into one vessel, a solution was obtained in the amount of X + X + 2 = 2 * X + 2;
The salt content in it: 0.2 * X + 0.5 * X + 1 = 0.7 * X + 1;
Let’s make the equation:
100% * (0.7 * X + 1) / (2 * X + 2) = 40%;
0.7 * X + 1 = 0.8 * X + 0.8;
0.1 * X = 0.2;
X = 2L;
The second vessel contained X + 2 = 4 liters of solution.