First find the number of substitute teachers left after half quit: 60 teachers / 2 = <<60/2=30>>30 teachers

Then find how many teachers quit after an hour but before lunch: 30 teachers * 30% = <<30*30*.01=9>>9 teachers

Then subtract that number from the number of teachers left after one hour to find how many are left after lunch: 30 teachers - 9 teachers = <<30-9=21>>21 teachers

# Answer

21
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
50% of substitute teachers walk out after 1 hour of teaching. 30% of the remainder quit before lunch. If 60 substitute teachers show up at 7 AM, how many will be left after lunch?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
21
50% of substitute teachers walk out after 1 hour of teaching. 30% of the remainder quit before lunch. If 60 substitute teachers show up at 7 AM, how many will be left after lunch?
train