Four? Isn't it stated in the question? Unless I am assuming wrong.
I believe it is 1500
(1920 - 420)
Answer:
Option b is correct
.
Step-by-step explanation:
Domain is the set of all possible values of x where function is defined.
Given the function:

To find the domain of the given function:
Exclude the values of x, for which function is not defined
Set denominator = 0

By zero product property;
and 
⇒x = 0 and 
⇒x = 0 and 
Therefore, the domain of the given function is:

You would round down to 25,000
Answer:
x=6
b= 126
Step-by-step explanation:
8x+78 = 2x+114
8x-2x = 114-78
6x=36
x=6
--------
b=2x6+114
b= 126