A, b and c stand for 3 different numbers.
the mean of a and b is 40.
the mean of b and c is 35
a+b+ c
calculate all their values.

The mean is x amount of numbers added together divided by x. Since both mean questions have only 2 numbers, you times 40 and 35 by 2 to reverse the question. 

40 X 2 = 80 = a + b. 
35 X 2 = 70 = b + c. 
100 = a + b + c

80 and 70 are quite close together.  Therefore, b would probably be around 40 - 60.  I used trial and error to work out the answer. 

b = 40
80 - 40 = 40.  
a = 40. 
70 - 40 = 30. 
c = 30. 
40 + 40 + 30 = 110. 
THIS ANSWER IS WRONG. 

b = 50. 
80 - 50 = 30. 
a = 30. 
70 - 50  = 20.
c = 20. 
50 + 30 + 20 = 100. 
THIS ANSWER IS CORRECT. 

a = 30
b = 50
c = 20