Question 358986
This is a problem on inverse variation.  The no. of days D to finish the work is inversely proportional to the number of hours worked h and the number of people p working.  Thus {{{D = k/(p*h)}}}, where k is a proportionality constant.
{{{9 = k/(9*9) = k/9^2}}}, so that {{{k = 9^3 = 729}}}.
Then {{{D = 729/(8*8) = 729/64 = 11.39}}} hours.