Assuming that you are asking for the variance of a population, the formula to calculate variance is:
σ^2 = Σ(x_i - μ)^2 / N
where μ is the mean of the population and N is the number of items in the population. In this case, we are given that σ (standard deviation) = 5. We can rearrange the equation to solve for μ:
μ = Σx_i / N - σ^2 / N
Now that we have μ, we can plug it back into the original equation to solve for σ^2:
σ^2 = Σ(x_i - μ)^2 / N
= Σ(x_i - (Σx_i/N - σ^2/N))^2 / N
= Σ((x_i - Σx_i/N)*(1 + σ^2/N)) / N
= (1 + σ^2/N)*Σ(x_i - Σx_i/N)^2 / N
= (1 + σ^2/n)*variance