Hint: Here we will take the given expression and open the bracket and will solve accordingly. Since there is a positive sign outside the bracket therefore there will be no change in the sign of the terms inside the bracket. Apply this concept and solve accordingly for the resultant required value.
Complete step-by-step solution: Take the given expression: $6 + ( - 6)$ Open the bracket given in the above expression, remember when there is a positive sign outside the bracket then the sign of the terms inside the bracket does not change. Positive terms will remain positive and the negative term will remain negative when brackets are opened and hence, there is no change of the sign of the terms. $6 + ( - 6) = 6 - 6$ Like terms with the same value and opposite sign cancel each other. $6 + ( - 6) = 0$ This is the required solution.
Additional information: Be careful about the sign while doing simplification among the like terms. i) Addition of two positive terms gives the positive term ii) Addition of one negative and positive term, you have to do subtraction and give signs of bigger numbers, whether positive or negative. iii) Addition of two negative numbers gives a negative number but in actual you have to add both the numbers and give a negative sign to the resultant answer.
Note: Since there was a positive sign outside the bracket there was no change in the sign of the terms inside the bracket but when there is a negative sign outside the bracket then there will be a change of sign for all the terms inside the bracket while opening the bracket. Positive terms become negative and the negative term becomes positive.