hope it will help u..........
Answer:
Option C is correct.

Step-by-step explanation:
Given the expression: 
Using properties of summation:
Using properties of summation in the given expression we have;
= 
=
Therefore, the following given expression uses the properties of summation to represents is, 
Answer:
2
Step-by-step explanation:
25+5*? = 35
? = 2
Answer:
40
Step-by-step explanation:
5 people in the room have 5*40 = 200 years altogether
a new person is X years old.
Now 6 people have (200 + x) years altogether.
Mean age of 6 people is (200+x)/6. and it is also = 40.
So,
(200+x)/6 = 40
200 + x = 240
x = 40