Hi Audrey,
I like to help my students determine what operations to use in problems like these by changing the numbers from fractions to whole numbers. If Natalie was 60 inches tall, Marian is 1 inch shorter than Natalie and Jane 2 inches shorter than Marian, you would easily see that Jane is 3 inches shorter than Natalie. So you'd take 60 inches minus 3 to get Jane's height (57 inches). Follow this thinking to do your problem with fractions. Add together how much shorter Marian and Jane are then subtract that number from Marian's height.
1 1/6 + 1 1/3 = 2 1/2 (find common denominator of 6 for 1/6 and 1/3 and change 1/3 to an equivalent fraction using 6 as the denominator ... 2/6 add 1/6 + 2/6 to get 3/6 which when reduced is 1/2)
Now subtract 2 1/2 from 56 4/5
56 4/5 - 2 1/2 (Common denominator of 10 with equivalent fractions)
56 8/10 - 2 5/10 = 54 3/10 ... Jane's height
