P2715 ccj and zrz on the Way Home

zrz was walking on the way home, suddenly really needed to use the restroom, rushed to the restroom door, and was surprised to find an equation on it.

Given an expression ($a*b=c$ or $a/b=c$ or $a+b=c$ or $a-b=c$) where $a$, $b$, and $c$ are three numbers, but one of them is a question mark '?', meaning unknown, please find the unknown value.

A single line containing an expression ($a*b=c$ or $a/b=c$ or $a+b=c$ or $a-b=c$), which may contain extra spaces.

The number represented by '?', formatted to 2 decimal places.

The total length is less than 200. All numbers and the required number will not exceed 1000000000, and none are negative. The input numbers are integers (not decimals), but the answer may be a decimal. Translated by ChatGPT 5