Which of the following figures made it possible for doctors today to study these types of images of the human body? O George Washington Carver
O Charles Richard Drew
O Marie Curie
O Albert Einstein

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.

: -)

1. efficient use of space

2. elimination of groundwater contamination

3. energy generation

4. lower carbon footprint