To find the area of a rectangle, you multiply the length by the width. In this case, the left side of the poster is 7 units (which can be considered the length), and the top side of the poster is 6 units (which can be considered the width).
So, the area \( A \) is calculated as:
\[ A = \text{length} \times \text{width} = 7 , \text{units} \times 6 , \text{units} = 42 , \text{square units} \]
Therefore, the area of the completed poster is 42 square units.