the graph is a line, so the general equation of a line is
where m is the slope and b is the y-intercept(when the line touches the y-axis)
Y-intercept
from the graph we can notices the number on y-axis when the line touches it, is
then b=-3
now we replace b on the general equation
Slope
we can replace a point of the graph different to the y-intercept n this case I will use (-4,0)
then replace on general equation
simplify and solve for m
the slope is -3/4
Finally
we replace b and the slope on the general equation to find the line