@ AVIATROZ
True altitude = Indicated altitude + 4% of Indicated every 10 deg above ISA if ISA deviation is positive.
= Indicated altitude - 4% of Indicated every 10 deg below ISA if ISA deviation is negative.
Here 15000 is the true altitude. Temp is 15 deg lower so Indicated altitude will be higher. 4% for 10 deg so 6% for 15 deg.
6 % of 15000 is 900. So Indicated altitude is 15900.
The altimeter setting is 1003 so you will need to set 27 x10(1013-1003) = 270 feet higher.
15900 + 270 = 16170 feet which is your answer.
Hope you got it.