Your data seems to fit easily into the Slope Intercept form of the line, where m, the slope or angular coefficient is given. You need to solve for b in each case to get the equation of the line.
A=(1,-3) and m=3
y = mx + b
-3 = 3(1) + b
-3 = 3 + b
Subtract 3 from both sides of the equation to solve for b
-3 - 3 = b
-6 = b
The Equation of Line A is
y = 3x - 6
In Standard Form its
-3x + y = -6
A=(-2,1) and m=-1
y = mx + b
1 = (-1)(-2) + b
1 = 2 + b
Subtract 2 from both sides of the equation to solve for b
1 - 2 = b
-1 = b
The Equation of Line A is
y = -x -1 in Slope Intercept Form
In Standard Form its
x + y = -1
You give the last one a try.
A= (3,7) and m=-2
You can check you lines by graphing them at Desmos.com. You can also check them with the original coordinates by plugging in x to see if you get the corresponding y.
