Solve the system of linear equations
\left\{
\begin{array}{r@{}r@{}r@{}r}
x & + 2 y & -7 z = & -4 \cr
2 x & + y & +z = & 13 \cr
3 x & + 9 y & -36 z = & -33
\end{array} \right.
The solutions have the form x = a + bt , y= c + dt, z= t ,
where t is any real number.

Finda,b,c,d .
a =

b=

c =

d =

Find

In order to get credit for this problem all answers must be correct.