Obtain an equivalent system by performing the stated elementary operation on the system. Interchange equations 1 and 3. \[ \begin{array}{r} 5 x-8 y+5 z=3 \\ x-6 z=9 \\ 7 x-2 y+8 z=1 \\ 9 x-7 y+7 z=6 \end{array} \]

Step 1 ：Obtain an equivalent system by performing the stated elementary operation on the system.

Step 2 ：Interchange equations 1 and 3.

Step 3 ：The equivalent system after interchanging the first and third equations is: \[\begin{array}{r} 7 x-2 y+8 z=1 \\ x-6 z=9 \\ 5 x-8 y+5 z=3 \\ 9 x-7 y+7 z=6 \end{array}\]

Step 4 ：\(\boxed{\begin{array}{r} 7 x-2 y+8 z=1 \\ x-6 z=9 \\ 5 x-8 y+5 z=3 \\ 9 x-7 y+7 z=6 \end{array}}\)