How do you write 0.0036 in scientific notation

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).

Which value would be a solution for x in the inequality 47-4x< 7

Another type of subtraction equation is 16-b=7. explain how you would sole this equation then solve it.