Could someone explain how they worked this out as well please?

Arefrigeration system at your company uses temperature sensors fixed to read celsius (°c) values, but the system operators in your control room understand only the fahrenheit scale. you have been asked to make a fahrenheit (°f) label for the high temperature alarm, which is set to ring whenever the system temperature rises above –10°c. what fahrenheit value should you write on the label?

Find the maximum value of p= 4x + 5y subject to the following constraints :

Leonardo wrote an equation that has an infinite number of solutions. one of the terms in leonardo’s equation is missing, as shown below.