You've got 3 values there.
Get the sum of 65, 30 and 25 and divide their sum by the number of values that exist, which in this case is 3.

Answer:
40
Option C:
is the value of a and b
Explanation:
Given that the expression 
We need to determine the value of a and b
Let us consider the term
and take the prime factorization of the term 648
Thus, we have,
648 divides by 2,

324 divides by 2,

162 divides by 2,

81 divides by 3,

27 divides by 3,

9 divides by 3,

Thus, we have,

Therefore, equating the powers of 2 and 3, we get,

Hence, the value of a and b is 3 and 4
Thus, Option C is the correct answer.
Answer: 3
Step-by-step explanation: To find the sum of these two numbers, remember that adding a negative is exactly the same thing as subtracting a positive. In other words, when we see 18 + (-15), we can change the problem so it's easier to understand and we will change in to 18 - 15.
Now, this is just basic subtraction.
18 - 15 = 3
Therefore, 18 + (-15) = 3