Algebra nation question please help

The brain volumes (cm cubed) of 50 brains vary from a low of 904 cm cubed to a high of 1488 cm cubed. use the range rule of thumb to estimate the standard deviation s and compare the result to the exact standard deviation of 175.5 cm cubed, assuming the estimate is accurate if it is within 15 cm cubed

The price of an item has been reduced by 30%. the original price was $30. what is the price of the item now ?

If you are dealt 4 cards from a shuffled deck of 52? cards, find the probability that all 4 cards are diamondsdiamonds.