Answer: 13 feet.
Step-by-step explanation:
1. The formula for calculate the area of a parallelogram is shown below:
[tex]A=b*h[/tex]
Where [tex]b[/tex] is the base and [tex]h[/tex] is the height.
2. You know that the height f the parallelogram is 6 feet and the area is 78 ft². Therefore, you must solve for the base.
3. Then, the result is:
[tex]b=\frac{A}{h}\\\\b=\frac{78ft^{2}}{6ft}\\\\b=13ft[/tex]