The sum of a number and 4.5 is 8.2

Answer 1

 

 

 ?    +  4.5 = 8.2

 

Subtracts 4.5 from both sides

 

 ?  = 8.2 - 4.5

 

? = 3.7

 

So the missing number is 3.7

 

All in a day's work ;-)