Aslan1982,
[and I'm not picking on you]
The fact this question has been asked suggest to me that you need to delve more into the significance of that type of calculation ---
---on a CR3 it's two step process first find the TAS after alighning the appropriate windows for
Press. Alt and T then use that to find Mach number in the other window after aligning the
TAS
. and T in another window---
However, the parameters entered as well as the possible reasons for should be well understood far beyond the test question--for lack of understanding of a high speed high altitude environment---is a very dangerous situation---perhaps you need to delve a little deeper in to the theory--then ALL {pilot} calculations in aviation become very simple..because if you're ever in an extreme situation---these fact may help---but they definitely help to keep you out of that extreme situation in the first place----Mach is much much more than a test question-or a simple number that you get right for the exam----
it's compressibility, flutter, divergence, stalling, stability controllability, and overall structural survivability
et al.
PA