So first to find the length of board she had left we would have to find a common denominator for both fractions : 7/8 and 1/4.
The greatest common factor of both fraction is 8 so we would adjust 1/4.
Multiply both the numerator and denominator by 2 and you would get : 2/8.
Now we can easily subtract the fractions by just subtracting the numerators :
7/8 - 2/8 = 5/8.
So Jennifer has 5/8 of her board left.
Hope this helped!
