To find the area of the rectangular poster, you can use the formula for the area of a rectangle:
\[ \text{Area} = \text{length} \times \text{width} \]
In this case, the length of the poster is 7 units and the width is 6 units.
So, the area is:
\[ \text{Area} = 7 \times 6 = 42 \text{ square units} \]
Therefore, the area of the completed poster is 42 square units.