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.