The problem in the image is written in Japanese and can be summarized as follows:

• Container A has 400 mL of milk.
• Container B has an unknown amount of coffee (let’s call it $x$ mL).
• 200 mL of coffee is taken from container B and added to container A.
• After this, the ratio of the amount of coffee in container A to the amount of coffee remaining in container B becomes 5:2.

The question is asking: How much coffee was originally in container B?

Steps to solve:

1. Before mixing:

   • Container A: 400 mL milk, 0 mL coffee.
   • Container B: $x$ mL of coffee.

2. After transferring 200 mL of coffee from B to A:

   • Container A: 400 mL of milk, 200 mL of coffee.
   • Container B: $x - 200$ mL of coffee.

3. Final condition (ratio of coffee):

   • The amount of coffee in A to the remaining coffee in B is 5:2. This gives the equation: $\frac{200}{x - 200} = \frac{5}{2}$

4. Solving the equation:

   • Cross-multiply: $200 \times 2 = 5 \times (x - 200)$ $400 = 5x - 1000$
   • Solve for $x$: $5x = 1400$ $x = 280$

Thus, the original amount of coffee in container B was 280 mL.

Would you like further clarification on any steps?

Here are 5 related questions for further practice:

1. What would happen if you transferred 300 mL of coffee instead of 200 mL?
2. How would the ratio change if container A initially had 500 mL of milk?
3. What if the final ratio was 3:1 instead of 5:2?
4. How much coffee would need to be transferred to make the ratio 4:3?
5. What is the final amount of liquid in container A after the transfer?

Tip: Always check the units when dealing with mixture problems, to ensure consistency across all quantities.