What do water, aluminum, redwood trees, and valley quail all in common?

Water, aluminum, redwood trees, and valley quail can be found anywhere on Earth. Water is everywhere, aluminum is a rich metal, trees are everywhere, valleys are everywhere.

a charge 3q is at the origin, and a charge −2q is on the positive x axis at x=a. part a where on the x-axis would you place a third charge so it would experience no net electric force? enter an expression for the exact answer, which will involve a square-root sign. (do not enter an approximate decimal answer.)