well the answer isn't exactly 3 feet, but it's very close at 2.91
first we convert all values to decimals to save time.
to convert a mixed number to a decimal you divide the numerator by the denominator and put the whole number in front of it
now we subtract the original value (7 7/8 or 7.875) from all the cut pieces to find out how much is left.
and there you go.