Can someone help me? I really dont understand this and I need to get it done soon qwq

In the field of thermodynamics, rankine is the unit used to measure temperature. one can convert temperature from celsius into rankine using the formula c= r/1.8 - 273, what is the temperature in celcius corresponding to r degrees rankine.

How do you determine whether a relationship represented as as graph is linear or nonlinear

We just started the introduction into circles and i have no idea how to do this.