Reverse the numbers that you chose and subtract the smaller number from the larger number.

The result will always be 198. For example, 123 would become 321; subtract 123 from 321, and the answer is 198.

Try it and see for yourself.

The diagonal belt of stars on the Hertzsprung-Russell diagram stretching from the high temperature and luminosity region of the diagram down to the low temperature end.

A star's position in the belt depends on its mass, and once on the Main Sequence a star remains there for most of its existence.

The point on the Hertzsprung-Russell diagram occupied by a star that has a core temperature high enough for nuclear reactions.