4.23 + (-8.79)= - (8.79 - 4.23) = - 4.56
-4.56 + (-6.23)= - (4.56 + 6.23) = - 10.79
-10.79 + 9.79= - (10.79 - 9.79) = - 1
-1
4.23+(-8.79)= -4.56
-4.56+(-6.23)= -10.79
-10.79+9.79= -1
