For example:
int number = scanf("%d", &number);
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The return value of scanf is the number of items assigned. So, when successful, scanf("%d", &number) returns 1. Then int number = scanf("%d", &number); says to initialize number to 1. That is not what you want.
int number = scanf("%d", &number); also tells scanf to store the result of converting a decimal numeral from input in number. Which happens first, storing the conversion result or storing the return value? Interpreting this gets into a mess with the C standard. It is not worth figuring that out, because you just should not write code like this.
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