Answer:
a=-4.3
Why?:
You would have to keep the answer negative, this is because if it were to be positive it would make the negative decrease.
You could easily get a line paper and line up-
-4.3
+ -1.2
_______
-5.5
-5.5-(-1.2) would make the equation end up like -5.5+1.2, and -5.5+1.2=-4.3
Therefore,
a=-4.3