30% of the 30 marbles is nine and 9-30 = 21 so your answer is 21
4 consecutive odd numbers....x, x + 2, x + 4, x + 6
2(x + x + 2) = 3(x + 4 + x + 6) - 40
2(2x + 2) = 3(2x + 10) - 40
4x + 4 = 6x + 30 - 40
4x + 4 = 6x - 10
4x - 6x = -10 - 4
-2x = - 14
x = -14/-2
x = 7
x + 2 = 7 + 2 = 9
x + 4 = 7 + 4 = 11
x + 6 = 7 + 6 = 13
ur numbers are : 7,9,11,13 <==
Answer: x=3
work: x+9=12
x=12-9
x=3
Answer:

Step-by-step explanation:

Putting x = 1
=> 
Given that f(1) = 1
=> 
=>
-------------------(1)
Now,
Putting x = 2
=> 
Given that f(2) = 5
=> 
=> 
=>
----------------(2)
Subtracting (2) from (1)

For b , Put a = 9 in equation (1)
