I am trying to do this question with out derivatives for about 45 min and i still don't know what to do. any help would be appreaciated. Thank you.

find the coordinates of the point on the point on the curve f(x)=3x^2 -4x where the tangent is parallel to the line y=8x.

I know that the slope of the tangent is 8, but i am not sure how to proceed.