Fractions, Help!

Why do you multiply 75 over 2 by 4 over 43 to divide 37 and 1 over 2 by 10 and 3 over 4?

(Why do you multiply 75/2 by 4/43 to divide 37 1/2 by 10 3/4?)

Ameteorologist is studying the monthly rainfall in a section of the brazilian rainforest. she recorded the monthly rainfall, in inches, for last year. they were: 10.4, 10.3, 11.7, 11.1, 8.0, 4.4, 2.6, 1.8, 2.5, 4.4, 7.3, 9.5 fill in the missing values in the formula. what is the variance?