I figured out the first but am struggling with the second

Question

A roast turkey is taken from an oven when its temperature has reached 190 Fahrenheit and is placed on a table in a room where the temperature is 70 Fahrenheit. 

(a) If the temperature of the turkey is 150 Fahrenheit after half an hour, what is its temperature after 45 minutes?  Fahrenheit. 

(b) When will the turkey have cooled to 105 Fahrenheit?  hours. 

Answer 1

I am not sure whether you were required to solve the differential equation associated with Newton's Law of Cooling or not, but I will start there.

Newton's Law of Cooling states that the rate at which an object cools is described by the equation:

dT/dt=k*(T-T_amb). This is a separable DEq and, since you answered part a), you have solved this equation for T(t), including for the constant k.

For part b) just set T(t)=105 and solve for t.