Answer: 40%
Step-by-step explanation:
This represents this equation:
70*x =28
x=28/70=0,4
Multiply that with 100 to get the percentage.
A would be fine as your answer.
Yes that is right
x=-4 is a vertical line passing through the points (-4,y)
where y can be any value
Answer:

Step-by-step explanation:
Find distance between B and market: |B-M|=|M-B|
Distance between A and B:
, call this equation (1)
Distance between A and market
, call this equation (2)
Solve (1) - (2)

The hypotenuse length is √(4*4 + 3*3) = 5 (not √7 I suppose)
The area is base*half height = 4*3/2 = 6.
In short, I don't think complex numbers really interfere here.