What is the first step in solving the equation
x^2-16/25=0
What is the second step in solving the equation?

This is so hard and it’s for a test

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

Acircle has a circumference of 28.36 units what is the diameter of the circle