The concept that can be used in order to answer this item is that of the conservation of heat among the system. We let T be equal to the final temperature. The equation that would allow us to relate the initial and final conditions of both substances is as follows,
m₁cp₁(T - T₁) = m₂cp₂(T₂ - T)
The first entity, 1, is the milk and the second entity, 2, is the coffee. We are given that the specific heats of both substances are just equal so we can eliminate them from the equation. Substituting the known values,
(10 g)(T - 10°) = (1.60 x 10^2 g)(90° - T)
The value of T from the equation is 85.29°C.
Answer: 85.29°C
