Please help me with this!!

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

Simplify -4z+2y-y+-18z a.-22z+y b.-14z+2 c.3y+22z d.y +14z

Yo need asap pls ! markin da brainiest too !