7x = = 3 (mod 15)

take the gcd (7,15) = 1 therefore 1 and 1/3 are 2 incongruent solutions??

6x = = 5 (mod 15)

gcd = 3 but 3 isn't a divisor of 5 therefore there are no solutions??

x^2 = = 1 (mod8) I get 4 and 1 as two incongruent solutions??

I just want to see if my working is accurate...

THANK YOU