If a scientific idea has been proven 100% of the time, like gravity, it becomes a whereas an idea that is generally believed but has not been proven to be 100% true would be called a .

The correct answer would be - scientific theory.

Explanation:

A scientific theory is a confirmed explanation of any particular natural aspect or phenomenon of the world which is confirmed and accepted widely by the facts based on observation and experiment.

This particular idea or explanation for the natural phenomenon is true time based and believed to be true for time being and proved for a time but can be changed with the new discoveries and facts.

try using substitution:

x + y - 6 = x - y. (i'm not giving you the exact answer). since 0 = x - y, then sub 0 in the equation with x - y. combine your like terms, and then use inverse operations, and you'll have your answer.

: -)

thinking it would be d not too sure but i think it's right