The general form of an equation in slope intercept form is ;
y= mx + c where m is the gradient and c is the y-intercept
The equation given is : y = -9x-81 ------this means the slope is -9
This is determined from the general equation ;
y = m x + c
y= -9 x - 81
where -9 is the gradient
Because the two lines are parallel, it means the other equation should have a slope of -9, thus apply the formula for slope give point {-2,-8}
m= change in y-coordinates value / change in x coordinate values
-9 = y --8/x--2
-9 = y+8 /x+2
-9 {x+2} = y+8