In Problems 71-74, use the idea behind Example 15 with a graphing utility to solve the following systems of equations. Round answers to two decimal places.
$\left\{\begin{aligned} 25 x+61 y-12 z & =21 \\ 18 x-12 y+7 z & =7 \\ 3 x+4 y-z & =-2\end{aligned}\right.$