-3.2+(-4.6)+5.4
when you add a negative number it is the same as just subtracting it.
-3.2-4.6+5.4
-3.2-4.6 can be done like this: -(3.2+4.6) making it -7.8
-7.8+5.4
-7.8+5.4 can be done like this -(7.8-5.4) making the final answer-2.4
Hope this helps :)