Final answer:
To find two addition equations with a sum of -21.5, assign variables to each equation, and solve for the values. The two equations are -10 + (-11.5) = -21.5 and 8 + (-29.5) = -21.5.
Step-by-step explanation:
To find two addition equations with a sum of -21.5, we need to assign variables to each equation and solve. Let's call the variables x and y. The equations would be: x + y = -21.5 and -x - y = -21.5. In the first equation, let's assign a value of -10 to x, which means y would be -11.5. In the second equation, let's assign a value of 8 to x, which means y would be -29.5. Therefore, the two addition equations with the same sum of -21.5 are -10 + (-11.5) = -21.5 and 8 + (-29.5) = -21.5.