# How do you show that the temperature of the coffee after t minutes is 20 + 75e^(-kt) if a cup of coffee has a temperature 95 degree Celsisus and takes 30 minutes to cool to 61 degrees celsisus in a room with temperature 20 degrees celsisus?

I assume that the temperature $T$ must be a function of time given by an exponential decay of the type: $T \left(t\right) = A + B {e}^{- k t}$ where the constants must be given as in your formula because: