He had 40 before losing them into the sewer because 20 x 2 =<<40=40>>40

He started with 100 because 40/.4=<<100=100>>100

# Answer

100
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Archie is playing with his marbles outside. He loses 60% of them into the street. Of the remaining ones, he loses half down a sewer. If he has 20 left, how many did he start with?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
100
Archie is playing with his marbles outside. He loses 60% of them into the street. Of the remaining ones, he loses half down a sewer. If he has 20 left, how many did he start with?
train