Can someone please help me with these 3 questions

Answer:
1.) {Slope} Run=A Rise=B (any letter can be used instead of A and B.)
B=(x1,y1) A=(x2,y2)
B=(2,1) A=(0,-3)
Rise=4 Run=2 this creates 4/2
4/2=2
How to check your work:
m=x2-y2/x1-y1
m=1+3/0-2 (the negative in -3 changes to a positive so it's now addition. Without changing the appearence to addition, it would still mean the same thing, it would look like this, 1- -3 the two negatives cancel eachother out.)
1+3/0-2=4/2=2 (this is the same as the answer above so it's correct, 2 is the slope.)
Step-by-step explanation:
Slope=rise/run
Rise/run=y/x
Y/x=y2-y1/x2-x1
(Rise means how many units you move up or down from point to point. On the graph that would be a change in the y values. Run means how far left or right you move from point to point.)
Every straight line can be represented by y=mx+b
m=slope
b=y-intercept
Calculating y-intercept:
(The y-intercept is the value of y at the point where the line crosses the y-axis.)
The y-intercept is (0,-3) because that's where the line crosses.
I'm sorry if this is confusing, but I hope this helps you get the other two answers!