94. A system of five linear equations. Solve the following system of equations:

$$
\left\{\begin{array}{l}
x+y+z+u=5 \\
y+z+u+v=1 \\
z+u+v+x=2 \\
u+v+x+y=0 \\
v+x+y+z=4
\end{array}\right.
$$
94. By adding all five equations and dividing the result by 4, we get

$$
x+y+z+u+v=3
$$

Now it only remains to subtract each of the original equations from this equation in turn to obtain the desired solution $v=-2$, $x=2, y=1, z=3, u=-1$.