Why do you move the .0100 - x to the left side of the equal sign?

Calculate the mass of silver needed to react with chlorine to produce 126g if silver chloride?

If i initially have a gas at a pressure of 12 atm, a volume of 23 liters, and a temperature of 200 k, and then i raise the pressure to 14 atm and increase the temperature to 300 k, what is the new volume of the gas?

Chromosome 17 is made of over million base pairs.