Given: V_a = +125 V
V_b = -55.0 V
and q_p = +1e = +1.602\times10^-19\text(C)
The electric field does work on the proton much like the gravitational field does work on a mass. A mass falls from high potential to low potential, like a positive test charge in an electric field.
which becomes `W_(ba) = -\DeltaV_(ba)*q`
`-(V_b-V_a)*q = -((-55.0V)-(125V))*(1e) = 180 eV`
To get joules, we multiply by the actual charge.