Find the value of each missing variable

Average salary for a medical assistant is $31,220 which is a 20% income tax bracket how much money would they pay in income tax?

The contents of 3838 cans of coke have a mean of x¯¯¯=12.15x¯=12.15. assume the contents of cans of coke have a normal distribution with standard deviation of σ=0.12.σ=0.12. find the value of the test statistic zz for the claim that the population mean is μ=12.μ=12.

At which value in the domain does f(x) =0?