Adding negative numbers is same as subtracting those negative numbers. For example let us add - 5.6 and - 6.7
The expression can be written below
[tex]-5.6+(-6.7)=-5.6-6.7=-12.3[/tex]Notice that when addition sign multiplies the negative sign it becomes negative.
[tex]-37.27+(-13.2)=-37.27-13.2=-50.47[/tex]