Final answer:
To find (f+g)(-3), we add f(-3) and g(-3), getting 12 + (-7) which simplifies to 5. This result applies the rule of adding numbers with opposite signs.
Step-by-step explanation:
To find (f+g)(-3), we need to calculate the sum of the values of f and g at -3. We are given that f(-3) = 12 and g(-3) = -7. According to the rules for addition of numbers with different signs, we subtract the smaller number from the larger one, and the answer takes the sign of the larger number.
So, (f+g)(-3) = f(-3) + g(-3) = 12 + (-7) = 12 - 7 = 5.
This calculation applies the rule that when two numbers with opposite signs are added, we subtract the smaller number from the larger number and assign the result the sign of the larger absolute value.