Question

at what temperature does solid ice and liquid water coexist together

Answer 1

The temperature at which solid ice and liquid water coexist is 0.01 °C.

In the scientific term for this is called the triple point of water, because not only solid ice and liquid water but also water vapour exists together at this temperature.

There is also a technical term for this existence of all the three states of water called as thermodynamic equilibrium.

Answer 2

The single combination of pressure and temperature at which liquid water , solid ice, and water vapor can coexist in a stable equilibrium occurs at exactly 273.16 K (0.01 °C; 32.02 °F) and a partial vapor pressure of 611.657 pascals (6.11657 mbar; 0.00603659 atm).