Answer
Please see the figure attached.
Work Step by Step
The contour map of $f\left( {x,y} \right) = x + 2y - 1$ with level curves $c = - 8, - 6, - 4,...,4,6,8$ is obtained by plotting the lines:
$c = x + 2y - 1$ for $c = - 8, - 6, - 4,...,4,6,8$
The contour interval: $m=2$.
