:what’s the equation of a line that passes through points (0, -1) and (2, 3)?

First, start off by finding your slope. Your slope will be change in Y divided by change in X, which would be Y2-Y1/X2-X1.
3- -1/ 2-0
Since you're subtracting a negative, that turns into addition.
4/2 = 2
Now you know your slope is 2. Next you can use your equation y=mx+b to find your b, or your y intercept. You can use one of your two pairs of points to plug in x and y. Plug your slope in for m as well.

Y=mx+b
3 = 2(2) + b
3 = 4 +b
-4  -4
-1 = b

Now you can plug in your y intercept and slope for your equation!
Y=2x-1