 Hello and welcome to the session. In this session, we will discuss a question which says that the temperature dropped rapidly overnight, starting at 85 degrees Fahrenheit, the temperature dropped at 5 degrees per hour, write an expression for the temperature T in degrees as a function of number of hours h. Now before starting the solution of this question, we should know a result. And that is, any linear expression is of the form y is equal to n x plus b. Now this result will work out as a key idea for solving out the given question. Now let us start with the solution of the given question. Now here we are given, what is the description of the function? We are given initially the temperature was 85 degrees Fahrenheit, then it started decreasing at the rate of 3 degrees per hour. And here we have to write a linear expression for temperature and number of hours. And here temperature is noted by the variable T and number of hours are noted by the variable h. Now as temperature decreasing with hours, temperature depends on temperature T dependent variable and number of hours that are denoted by the variable h represent dependent variable. Now change in temperature, 3 degrees h number of hours the temperature is decreased by 3 degrees Fahrenheit from 85 degrees Fahrenheit. Now from the key idea we know that any linear expression is of the form y is equal to n x plus b whereby is the dependent variable x is the independent variable. Now here as T is dependent variable and h is the independent variable, the temperature T is decreased by 4 degrees Fahrenheit from 85 degrees Fahrenheit. So required linear expression is equal to 85 minus. Now here we are putting a minus sign because temperature is decreased from 85 degrees Fahrenheit or we can write as T is equal to minus 4 h plus 85. T represents the temperature. This is the required linear expression of the temperature T in degrees as a function of number of hours completes our session. Thank you all have enjoyed the session.