Which pair of radicals is a pair of like radicals

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.

In the coordinate plan (-6,9) b (3,9) c (3,3) def is shown in the coordinate plan below

Aline on the wall and a line on the floor are skew. always, sometimes, or never?