Donny saves a total of $15+$28+$13 = $<<15+28+13=56>>56 across all 3 days

He spends half of his total savings which is $56*(1/2) = $<<56*(1/2)=28>>28

# Answer

28
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Donny saves $15 on Monday, $28 on Tuesday and $13 on Wednesday. On Thursday he spends half of his total savings so far. How much did he spend?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
28
Donny saves $15 on Monday, $28 on Tuesday and $13 on Wednesday. On Thursday he spends half of his total savings so far. How much did he spend?
train