Final answer:
The sum of the expression (-21) + (-13) + 20 is -14. We add the two negative numbers together and then add the positive number, ensuring to keep the sign of the largest absolute value when the signs are different.
Step-by-step explanation:
To solve the given expression (-21)+(-13)+20, we have to follow the rules for adding and subtracting integers.
Firstly, let's look at the numbers with the same sign. We have -21 and -13, which are both negative. When we add two negative numbers, we add their absolute values together and keep the negative sign. So, -21 + (-13) becomes -21 + -13 = -34.
Now we have the sum of -34 and 20. Since these numbers have opposite signs, we subtract the smaller absolute value from the larger one and keep the sign of the larger absolute value. This translates to -34 + 20, which becomes -14.
The final solution to the expression (-21) + (-13) + 20 is -14.