=2x5
=10
If you have a certain type of calculator it could answer that question easy
Horizontal
The Axes. The independent variable belongs on the x-axis (horizontal line) of the graph and the dependent variable belongs on the y-axis
Answer: $0.70
Explanation: see picture
You can re-write this quotient this way :

What's inside the square root must be greater than or equal to 0, because the domain of the square root function is defined on R+ (which is [0,+∞))
In other word we must find x so that :

at the end we get
28(x-1) ≥ 0
28x - 28 ≥ 0
28x ≥ 28
x ≥ 1
So the answer is B, x ≥ 1