2) carbon dioxide is returned to the atmosphere primarily by the

Respiration of humans

Step-by-step explanation:

The return of it to the atmosphere is also possibly being caused by the decay of plants and animals, also known as the process of burning something.

both equations and proportions are better.

5=812a+9+3

step 1: simplify both sides of the equation.

5=812a+9+3

5=(812a)+(9+3)(combine like terms)

5=812a+12

5=812a+12

step 2: flip the equation.

812a+12=5

step 3: subtract 12 from both sides.

812a+12−12=5−12

812a=−7

step 4: divide both sides by 812.

812a /812 = -7/812

a= -1/116

so the answer is

a=   -1/116