A Normal distribution has mean µ = 61.6. Find it’s standard deviation if 20% of the values are greater than 70.

Determine whether the set of whole numbers is closed under addition. explain why the set is or is not closed. give an example.

Adepartment store purchases screen-printed t-shirts at a cost of $5 per shirt. they mark up the price 150% (making the selling price 250% of the store's purchase price) and put them on the sales floor. every month that a t-shirt doesn't sell, the store reduces the selling price by 25%.

Evaluate the expression for the given value of the variable 7a - 4a for a =8