Given inequalities:

We would be plotting the graph of each inequality combine their solutions.

We have the equation : x + y = 6 from the inequality
We need two points to draw thw boundary line. Hence:
When x = 0:

When y = 0:

We have the points : (0,6) and (6,0)
Now that we have the boundary line points, we can show the region that satisfies the inequality as shown below:
The shaded region is the solution to the inequality
Similarly for the second inequality:

We need two points to draw the boundary line: x + 2y = 8. Hence:
When x = 0:

When y = 0:

We have the points: (0,4) and (8,0)
Now that we have the boundary line points, we can show the region that satisfies the inequality as shown below:
The shaded region is the solution to the inequality
Combining the solutions, we have:
Hence, the graph that best represents the solution to the system of inequalities is the graph in Option D
Answer: Option D