Answer: 
Step-by-step explanation:
It is important to remember the following:

In this case you can observe in the figure that "x" is an Angle formed by two chords, therefore, you can find its value applying the formula.
Therefore, the value of "x" is this:

First of all, you would use the FOIL method for -5(a + 3). This means to just multiply -5 to all of the values in the parenthesis. This would equal:
-5a -15 = -55
Then after, you would add 15 for both sides and get -5a = -40
Divide by -5 on both sides, you get a = 8.
Here is a visual representation: https://puu.sh/zPxLC/a16740d0ce.png
7-12 is like a negative number so it will be -5. And 13-18 would be -5 also.
Answer: Division property of equality
Step-by-step explanation:
Answer:
a. $60
b. it doesn't show how much Mark makes on here so I can't give an answer