Nitrogen is changed into which substances before being used by living things

nitrogen can be changed into macromolecules like proteins and nucleic acids (DNA and RNA)

Explanation:

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.

: -)

it would lead to upper respiratory infections and pneumonia.