Anything ! but right answer gets brainilest

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

Can someone me with #s 8, 9, and 11. with just one of the three also works. prove using only trig identities.

Solve for x: 5/3 x = 20/21 it's fraction. remember to simplify your fraction