Calculate the value of the question mark based on the pattern.

Solution:

1. The first line shows one cow equals 300 kg.
2. The second line shows three goats equal 150 kg. This means one goat equals 150 kg / 3 = 50 kg.
3. The third line shows two goats plus one buffalo equals 250 kg. Since one goat is 50 kg, two goats are 100 kg. Therefore, one buffalo equals 250 kg - 100 kg = 150 kg.
4. The last line shows one goat, one cow, and one buffalo.
5. Substituting the known values: 50 kg (goat) + 300 kg (cow) + 150 kg (buffalo) = 500 kg.

Answer: 500 kg