If you weigh 690n on the earth, what would be your weight on the surface of a neutron star that has the same mass as our sun and a diameter of 19.0 km ? ]

-- If you weigh 690N on the Earth, then your mass is about

           (690N) / (9.8 m/s²) = 70 kg .

-- If your mass is 70 kg then your weight on that neutron star would be

              G  M₁  M₂  /  R²

         =  (6.67 x 10⁻¹¹ N m²/kg²) (70 kg) (1.989 x 10³⁰ kg) / (19,000 m)²

         =  (6.67 x 10⁻¹¹ x 70 x 1.989 x 10³⁰) / (3.61 x 10⁸)        N

         =  (6.67 x 70 x 1.989 x 10¹⁹)  /  (3.61 x 10⁸)          N

         =    2.57 x 10¹³    Newtons .

  (about  2,890,000,000 tons !)

Alinear relationship would look like a straight line on the graph. it could have a positive negative or 0 slope. so it could be a line potentially going in any direction but it must be perfectly straight.