Hello there! 
x + 4.5 = -7.75 
The first step is to subtract 4.5 on both sides 
x + 4.5 - 4.5 = -7.75 - 4.5 
x = -12.25 
(Note: When you have two negative numbers, you add them and then keep the negative sign.) 
Let me know if you have additional questions. 
~Happy Studying~