Final answer:
The correct answer is Option D. To find the third number, we need to calculate the sum of all three numbers and then subtract the sum of the given two numbers from the average of the three numbers.
Step-by-step explanation:
To find the third number, we need to calculate the sum of all three numbers and then subtract the sum of the given two numbers from the average of the three numbers. The third number can be found using the formula:
Third Number = Average of Three Numbers - Sum of Given Numbers
Let's substitute the given values into the formula:
Average of Three Numbers = 70
Given Numbers = 105 + 40 = 145
Third Number = 70 - 145 = -75
Since the third number cannot be negative in this context, it is not possible to determine the third number using the given information. Therefore, the correct answer is:
d. 75