First add the time spent waiting for the first bus to the time spent on it: 12 minutes + 30 minutes = <<12+30=42>>42 minutes

Then divide that time by 2 to find the time she spends on the second bus: 42 minutes / 2 = <<42/2=21>>21 minutes

# Answer

21
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
To get to the library, Jill spends 12 minutes waiting for her first bus, 30 minutes riding on her first bus, and half the combined wait and trip time on her second bus. How many minutes does her second bus ride take?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
21
To get to the library, Jill spends 12 minutes waiting for her first bus, 30 minutes riding on her first bus, and half the combined wait and trip time on her second bus. How many minutes does her second bus ride take?
train