ANSWER
4/7
Step-by-step explanation
Mariana wants to put 6 3/4 feet of border across the top of a wall.
She has 3 6/7 of border.
To find the fraction of the project she can complete, we will simply divide the border she has now by the one she needs for the project.
First let us convert the fractions to improper fraction.
6 3/4 = 27 / 4
3 6/7 = 27 / 7
So we have that:
She can complete 4/7 of the project.