The opposite of a number or a variable is the number or variable written with a negative sign.For example opposite of 4 is -4.Opposite of x is -x.
The question is first asking us to write opposite of variable k.
The opposite of k is -k.The question is then asking us to find the sum of k and the opposite of k .That is k+(-k)= k-k =0
When two opposites are added the result is 0.