The answer is 12.5 ft. This is because 4% is technically 4/100 and we can simplify that to 1/25. After that we can use the proportion method by doing -
1. 6
—- = —-
25. X
The reason why we put 6 in the numerator section is because 6 inches is the 4%. After that we know that to get to 6 we need to do 1 x 6 and whatever we do to the top and have to do to the bottom. So 25 x 6 is 150 inches. However the question is saying converting it to feet, and we know that 12 inches is 1 feet. So we do 150 divided by 12 to get 12.5 feet.
Hope this helped!
~Alex