How many numbers are in the list $$ 2.5, 5.5, 8.5, 11.5, \ldots, 80.5, 83.5? $$
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
How many numbers are in the list $$ 2.5, 5.5, 8.5, 11.5, \ldots, 80.5, 83.5? $$
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
28
How many numbers are in the list $$ 2.5, 5.5, 8.5, 11.5, \ldots, 80.5, 83.5? $$
train