C(x)=15.00+0.20x= how to solve

Which of the following system of equation is not equal to the system of equations is not equal to the system of equations shown below

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

Icould really use some with this question.