An equation of a straight line in a coordinate plane which has the slope "m" and passes through the given point P = (a,b) is y - b = m*(x-a). (1) ( MEMORIZE it !) Now substitute the given data m =, a= 1, b= -3 into equation (1), and you will get y-(-3) = . (2) or, equivalently, y + 3 = , or 5y + 15 = -3x + 3, or, finally 5y + 3x = -12.