I need help with slopes and doing this equation : y=mx+b ?!?!?! Dx

okay so i found the slope :) and now i have to determine the equation of the line but idk how to do that. so like this is one example:

(13,8) and (11,12) . . . the slope is -2 . now i need help with the y=mx+b thing. i dont understand what to do for that.

y = mx + b

You already have the slope as -2, so we can now write

y = -2x + b

Next, we need a value for b.

If a point is said to be "on the line", then the values of its coordinates must satisfy the equations.

Fancy words to say : put the values in the equation, and the equation must balance.

One point is (x, y) = (13, 8)
(points are always given in the format (x, y) unless you are specifically told otherwise)

This means that, at that point, x=13 and y=8
If that point is on the line, then the equation must work at that point

y = -2x + b
8 = -2(13) + b
8 = -26 + b
8 + 26 = b
34 = b

then the equation can be written as

y = -2x + 34

You can now check by using the other point
(x, y) = (11, 12)

12 = -2(11) + 34
12 = -22 + 34
12 = 12
yep! it works.

Final answer, for the million dollars, Regis:

y = -2x + 34

You need to substitute the values for x and y in your equation. You choose any point, so use (13,8).
You know m=-2

y=mx+b
8=(-2)(13)+b

Know you can isolate b:

b= 8- (-2)(13)= 8- (-26)=8+26=34

And with b you can do the equation:
y=mx+b
y=-2x+34