What does the crossing over rule essentially help us figure out? In chemistry

How many moles of magnesium is 3.01 x10^22 atoms of magnesium?

Suppose you have designed a new thermometer called the x thermometer. on the x scale the boiling point of water is 129 ? x and the freezing point of water is 13 ? x. part a at what temperature are the readings on the fahrenheit and x thermometers the same?

An object displaces 652 ml of water. the volume of the object is: 0.652 cm³ 6.52 cm³ 65.2 cm³ 652 cm³