I can't tell if that is a question but I will answer it anyway:
An exterior of a shape is the lengths and angles outside of the shape.
An interior are the lengths and angles inside a shape.
Hope this helps.
Answer:
a) XT
c)ZS
I don't know of the b one
2 1/3
You would do 6 3/4- 1 3/4=5
5-1 1/3= 2 2/3
1/6 of a mi - 1 day, 2/6 of a mi- 2 days, 3/6 of a mi- 3 days, 4/6 of a mi- 4 days, 5/6 of a mile - 5 days, 1 mile - 6 days, 1 1/6 mi - 7 days, 1 2/6 mi - 8 days , so on & so forth, do you understand ?