In general, a solution of a system in two variables is an ordered pair that makes BOTH equations true. In other words, it is where the two graphs intersect, what they have in common. So if an ordered pair is a solution to one equation, but not the other, then it is NOT a solution to the system
Since you have y alone on one side of the equation......
Use substitution and plug in 1/2x-4 for y in the other equation.

Distribute

Combine like terms

Add 8 to both sides

Divide by 4
and 
Plug this value in for x

Simplify

Multiply everything by 8 and simplify

Divide.....

Your answers are:

Step-by-step explanation:
1. x: (-12, -13) y: (12, 13)
2. x: (4 ,9) y: (-4, -9)
3. x: (-10, 8) y: (10, -8)
Answer:
Step-by-step explanation:
-4
It’s similar to D because they are going to have the same measured angle