Arithmetic Formatter Help

I need help with Arithmetic Formatter. I have finished the writing the project but it gives me a traceback

Your code so far

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Challenge: Arithmetic Formatter

Link to the challenge:

it seems you have a syntax error because you are using the same quotes around the string and inside the string, so you have effectively the - operand between two strings, which is not a valid thing to use on strings

you need to change quote type or escape the quotes around the mathematical operators

I have changed the quote types, but it gives the traceback of assertion error

I see Syntax error: unmatched ')'

if you look at the error it also says where

Thank you for your help. I have just finished it.
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