The slope intercept form is
y = Mx + b
x and y are the coordinates, and m is the slope. If you don’t have b, you can plug in the other numbers you do have.
EXAMPLE:
A line has a slope of -3 and a coordinate of (1, 6). What is the y-intercept (b)?
y = Mx + b
6 = -3(1) + b
6 = -3 + b
9 = b