The "intercept form" of the equation for a line is ...
... x/a + y/b = 1
where a and b are the x- and y-intercepts, respectively.
Dividing by -15 will put your equation into this form:
... 3x/-15 + 5y/-15 = 1
... x/(-5) + y/(-3) = 1
Your graph will go through the points (-5, 0) and (0, -3).
