The relatively constant internal environment in the body is

download the app called socratic on your phone

answer; i believe that the correct answer is (light);

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.

: -)

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