How do i find the population standard deviation of dataset

Find solution of the linear equation y = 2/3x + 1/3

Write the factored form of this trinomial 9x^2+18x-7

The coverage of a base station of a telecommunication company forms a disk with a radius of (kilometers). let be the distance of a cellphone from a base station. assume that the location of cellphones in use are randomly uniformly distributed within the disk. calculate the mean and variance for the random variable.