asking for help because I can't figure this one out?

Question

A positron (a particle with a charge of +e and a mass equal to that of an electron) that is accelerated from rest between two points at a fixed potential difference acquires a speed of 9.0 x 10^7 m/s.
What speed is achieved by a proton accelerated from rest between the same two points? (Disregard relativistic effects.) Answer in m/s.

Answer 1

Relative mass:
Neutron = 1
Proton = 0.99862349
Electron = 0.00054386734
v ≈ √0.00054386734*(9.0 x 10^7)^2/0.99862349
v ≈ 2,100,333 m/s