In order to calculate the final temperature, we will need to use the heat formula below:
Where Q is the heat, m is the mass, c is the specific heat and DeltaT is the change in temperature.
The heat lost by the hot water will be received by the cold water, so we can write the following equation and solve it for T:
![\begin{gathered} Q_1=-Q_2\\ \\ 3\cdot c\operatorname{\cdot}(T-80)=-5\operatorname{\cdot}c\operatorname{\cdot}(T-5)\\ \\ 3T-240=-5T+25\\ \\ 3T+5T=240+25\\ \\ 8T=265\\ \\ T=33.12\text{ \degree C} \end{gathered}]()
Therefore the final temperature is 33.12 °C.