You accidentally plugged in 6 instead of 7 for .
Now that last line is essentially asking: "What is the remainder after 43 is divided by 17?"
How do I solve:
tr^(-a) ≡ m (mod p)
t = 6
r = 7
a = 6
p = 17
6*7^(-6) ≡ 0.000050999 (mod 17)
This obviously isn't right?
Edit: Sorry, I typed t = 7, it should have been t = 6, now corrected, and the -a should be ^(-a) due to a copy-paste which I neglected to check if copied itself correctly, apparently it did not, sigh.