Use Newton's second law.
The object's mass is the same everywhere, so first compute the mass using the object's weight on Earth:
F = ma ⇒ 59 N = m (9.8 N/kg) ⇒ m ≈ 6.02041 kg
Now compute the acceleration on the other planet:
F = ma ⇒ 40.5 N ≈ (6.02041 kg) a
⇒ a ≈ 6.72712 m/s² ≈ 6.7 m/s² ≈ 1.5g
where g = 9.8 m/s², just to express this acceleration relative to the gravitational acceleration at Earth's surface.
