9:1 because you divide both sides by 8. Hope this helps :)
36:21 in simplest form is 12:7, because 3 goes into both 36 and 21. Simplifying ratios is essentially the same thing as simplifying fractions. Once we have 12:7, we can't reduce any further, because 7 is prime.
Hope this helps!
Rewrite the fractions to have a common denominator to find the difference:
2/3 = 4/6
Difference = 4/6-5/6 = -1/6
Sequence formula = an = a1 + d(n-1)
A1 is the first term 5/6
And d = -1/6
Sequence = 5/6 -1/6(n-1)
Simplify to get an =(-n +6)/6