Questions

By trial and error method,

P=0, Q=9, R=0 satisfies the values.

The Length of the Day is determined in Astronomical Units.

The length of a day corresponds to the time the Earth takes to turn around on its axis, which is approximately 24 hours. But it's not exactly 24 hours. 

This phenomenon is due to tides raised by the Moon which slow Earth's rotation. Because of the way the second is defined, the mean length of a day is now about 86 400.002 seconds, and is increasing by about 1.7 milliseconds per century.

The letter 'X' resembles the same as the tool AXE in sounding.

Hence, the alphabet X is a tool.

One word substitution for Be the embodiment or perfect example of is Personify. Personify means represent or embody (a quality, concept, etc.) in a physical form.

Characterise: describe the distinctive nature or features of.

Idol: an image or representation of a god used as an object of worship.

Signify: be an indication of.

Chloroplasts use energy from light to transform carbon dioxide and water into sugar and oxygen.

A green pigment located in membranes within the chloroplasts of plants and algae and in the membranes of certain prokaryotes.