z <- rnorm(1000000) mean(z[z >= 1]) # 1.527304 mean(z^6) # 15.09554 qchisq(0.05, df = 6, lower.tail = FALSE) # 12.59159 A <- matrix(c(3, 4, -2, 1, 2, -1, 7, -2, 6, 2, -1, 1, 1, 6, -2, 5), nrow=4, ncol=4, byrow=TRUE) solve(A, c(9, 13, 11, 27)) # 1 2 3 4