The attachment shows my working. This can be done by using the formula for mixtures —>
Energy lost = energy gained. In this case, the energy lost by the alcohol is gained by the water.
Sooo, the formula for heat energy is mcΔt,
So you go
McΔt (alcohol) = mcΔt (water)
And then algebraically solve for C.
Refer to my working for the answer. Cheers!!