Finding Airspeed: Pressure Altitude, Temp & Mach Number

[physics_197]

Homework Statement

Pressure altitude of 12km,
Ambient temp is 15 celsius above that of the standard atmosphere,
cruise mach number is 0.85.

Find equivalent airspeed, total pressure at pitot tube, correctly calibrated airspeed, and incorrectly calibrated airspeed (Compression is ignored).

Homework Equations

Veq = sqr(sigma)*V
M = V/a
T = Tsea + a(h-hs)

The Attempt at a Solution

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Here is my process, please correct if needed, I took the altitude and found out what the temp should be. Then do I go and find sigma by using this temp I just found or use the 15 degrees above it? Then I should be able to use Mach to find the true airspeed and plug those into the eqn to find Veq.

And then, what is the difference between correct and uncorrect? The notes are very bare in these terms.

Thanks, feel free to ask questions!

 

[NascentOxygen]

Can you provide a reference to an online treatment of this topic?