TAT = SAT (1+0.2KrM^2)

Remember to put temperatures in Kelvin, and so...

 

225 = SAT x (1 + (0.2 x 0.85 x 0.7 x 0.7))

 

therefore SAT = 225 / (1 + (0.2 x 0.85 x 0.7 x 0.7))

 

= 225 / 1.0833

= 207.7 Kelvin

= -65oC.