<|im_start|>system
You are a helpful assistant. You first think about the reasoning process in the mind and then provide the user with the answer. You should try to truely solve the question by yourself without cheating.  <|im_end|>
<|im_start|>user
 A batch of feed can supply 10 ducks and 15 chickens for 6 days, or 12 ducks and 6 chickens for 7 days. How many ducks can this batch of feed supply for 21 days? Show your work in <think> </think> tags. And return the final answer in <answer> </answer> tags.<|im_end|>
<|im_start|>assistant
Let me solve this step by step.
<think>
user
5
A batch of feed can supply 10 ducks and 15 chickens for 6 days, or 12 ducks and 6 chickens for 7 days. How many ducks can this batch of feed supply for 21 days?
test