<|im_start|>system
You are a helpful assistant. You first thinks about the reasoning process in the mind and then provides the user with the answer.<|im_end|>
<|im_start|>user
Calculate the sequence to reach the puzzle target of 120 using the numbers 4, 5, 18, and 20. Only once arithmetic operation may be performed to combine these numbers in a way that satisfies the target. Display your equation in <think> </think> tags, and give the final equation in <answer> </answer> tags, resembling <answer> (4 / 2) + 18 - 5 = 18 </answer>.<|im_end|>
<|im_start|>assistant
Let me solve this step by step.
<think>