Louie got 100% - 80% = 20% of the total items incorrect, which is equal to 5 items.

So 1% is equal to 5/20 = 1/4 of an item.

Hence, the total number of items, represented by 100%, on the math quiz was 1/4 of an item x 100 = <<1/4*100=25>>25.

# Answer

25
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Louie obtained 80% on a math quiz. He had 5 mistakes. How many items were there on the math quiz?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
25
Louie obtained 80% on a math quiz. He had 5 mistakes. How many items were there on the math quiz?
train