So, the easiest one, the ratio of inches of rain to days is 9 inches to 30 days, or written (in ratio notation) as:
9:30
Simplifying this works just like a fraction (in fact, ratios are fractions and vice versa), so you could divide both sides by three (think of it as dividing the numerator and denominator by three) in order to get
3:10
And that is the most simplified form since 3 and 10 have no GCF greater than one. Hope I helped :)