Ice gains energy as it heats up from -15 to 0 degrees.
It's safe to assume that all of the ice then melts (due to the 59 degree starting temp. of "beaker water", and its greater mass). This also requires energy.
The melted "ice water" will then heat up to a certain temperature, T, where the "ice water" and "beaker water" are in thermal equilibrium.
All 3 of these processes require thermal energy from the "beaker water", as it cools from 59 to T degrees.
You can form a single equation involving T using this information.