need help with an instrument question

[aslan1982]

Hi can anyone help with these two questions. i just cant get the right answer

1.
fl310 cas 290kts coat = -48c what is the mach
ans = .78m

2.
f330 cas 340kts iaot = -19 what is the mach
ans = .975

if someone would be so kind to run through how to go about these that would be great

thanks in advance