Write an equation for the line in the given form. slope is -2 and (3,9) is on the line; standard form

Standard form?  That looks like either Ax + By + C = 0 or Ax + By = C.

I'll use the slope-intercept form first, and then convert my result to Standard Form.

y = mx + b, so here 9 = -2(3) + b    =>    9 + 6 = b = 15, so

y = -2x + 15.  Subtracting y from both sides, we get   0 = -2x - 1y + 15, 

or 2x + 1y = 15   (which has the form Ax + By + C).

It should be a or d i’m not sure