we have given that [tex] 3+(-3) [/tex] and [tex] (10.4)+(-10.4) [/tex].
we know that a property [tex] (a)+(-b)=a-b [/tex].
so [tex] (3)+(-3) [/tex] and [tex] (10.4)+(-10.4)=0 [/tex].
these number are called opposites because they have same value but opposite signs.
so the number and opposite of a number is added always equal to 0.