Question 1021498
Sasha worked by herself for 9 days. Matt helped the last 4 days. If he could finish the apartments alone in 22 days, then he did 4/22 of the total work. Sasha took 9+4 days to finish 22-4/22, or 18/22 of the work. So, she took 13 days to finish 9/11 of the work.
(9/11)/13=9/143 of the work done per day by Sasha.
143/9 days of work needed by Sasha to do the whole job by herself. ☺☺☺☺