This is the approach I used:

x - represents solution A quantity
y - represents solution B quantity

the first statement can be written 2x + y = 4% and the second one can be written as x + 2y = 3%
Then I found the lcm of 4% and 3% => 12%

3 ( 2x + y ) = 4 (x + 2y)
6x + 3y = 4x + 8y
2x = 5y
x:y = 5:2

=>

Assume the percentages of the two salt solutions A and B are a% and b%, respectively. We need to figure out the amount of salt for salt solution questions.

The amount of salt in 200g of solution A is 200*(a/100) = 2a. The amount of salt in 100g of solution B is 100*(b/100) = b.

After mixing the 2 solutions, the new solution is (2a + b) / 300 = 4/100, 100(2a + b) = 4(300), and 200a + 100b = 1200. Dividing everything by 100 gives us 2a + b = 12.

Then, the amount of salt in 100g of solution A is 100*(a/100) = a and 200*(b/100) = 2b.

After mixing the 2 solution, the new solution is (a + 2b) / 300 = 3/100, 100(a + 2b) = 3(300), and 100a + 200b = 900. Dividing everything by 100 gives us a + 2b = 9.

When we add two equations, we have (2a + b) + (a + 2b) = 12 + 9, 3a + 3b = 21 or a + b = 7.

Then we have a = (2a + b) - (a + b) = 12 - 7 = 5 and b = (a + 2b) - (a + b) = 9 - 7 = 2.

Therefore, A is the answer
Answer: A