So, these are actually pretty simple once you learn the equality used to solve for "x" and when to implement this method. You can use this equality to solve for a segment "x" anytime that two secant lines cutting through a circle come from the same point outside the circle.
Secant: by geometric definition is just a straight line that cuts a curve into multiple pieces.
I did one of them for you hopefully you can use my work for "a" to help you solve for "b".
For a. I got x=7.
Answer:
-3.5
The distance Rachel covers per hour is 3.5 miles
Step-by-step explanation:
After 2 hours, she is 13 miles from the campground.
After 4 hours, she is 6 miles from the campground.
Let x be the number of hours, y be the number of miles from the campground, then we have two points (2,13) and (4,6).
The equation of the line passing through the points
and
is

Substitute:

Hence,

The slope of the line is
and it represents that the distance Rachel covers per hour is 3.5 miles.