I am unsure how to solve this ,this is a practice sheet ​

What is the standard deviation of the following data set rounded to the nearest tenth? 3, 17, 18, 15, 12, 21, 9

To which sets of numbers does -12 belong? choose all answers that are correct. a) natural numbers b) integers c) real numbers d) irrational numbers

Plot a point at the y-intercept of the following function on the provided graph. 3y=-5x+7 20 points