2. Find the solutions of the following systems of linear congruences.
a)
$$\begin{array}{r}
2 x+3 y \equiv 5(\bmod 7) \\
x+5 y \equiv 6(\bmod 7)
\end{array}$$
b)
$$\begin{aligned}
4 x+y & \equiv 5(\bmod 7) \\
x+2 y & \equiv 4(\bmod 7)
\end{aligned}$$
2. a) $(x, y) \equiv(0,4),(1,1),(2,5),(3,2),(4,6),(5,3),(6,0)(\bmod 7)$
b) no solution