Umultiply these numbers ? or divide them

Determine the mean and variance of the random variable with the following probability mass function. f(x)=( 729divided by 91) (1 divided by 9) superscript x baseline comma x equals 1,2,3 round your answers to three decimal places (e. g. 98.765).

Select all of the following expressions that are equal to 2.5.

Can anyone explain to me how to do this? anything will .