As the two amounts of ethanol mix, energy is transferred from one to the other as heat, until an equilibrium temperature T is reached.
The formula for this heat transfer is
Q = mcΔT
Q is the heat, m is the mass, c is the specific heat of the material, and ΔT is the change in temperature.
Q = 25.0g * c * (T - 5.0 °C) = 50.0g * c * (75.0 °C - T)
Normally you'd need to know c, but since both are the same material, these cancel
25(T-5) = 50(75-T)
You can solve this fairly easily now for the final temperature T.