PLEASE HELP ME!! Geometry escape Challenge G

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

If f(x) = x+8 and g(x) = 4x- 3, find (f+g)(x)

What happens to the area as the sliders are adjusted? what do you think the formula for the area of a triangle is divided by 2?