A can do a piece of work in 20 days and B can do it in 12 days, B work for 9 days, in how many days A alone can do the work

Use the spider tool located on page 1 of this activity to draw a 12-pointed star for the new logo. (hint: if the spider rotates 360 degrees -- or 720 degrees or 1080 degrees -- she will be facing in the same direction in which she started. when the spider is done drawing, you want her to be facing in the same direction in which she started. she'll be making 12 rotations, all the same size, so each rotation must be some multiple of 360/12 = 30 degrees.) urgently. been stuck on this problem for around 45 minutes now.! it should be easy if you're smart enough