Option (a)
GIven:
The equation is,
[tex]9x+(-9x)+12=0+12[/tex]The objective is to identify the property which justifies the equation.
By comparing the LHS and RHS of the equation, the value of 9x+(-9x) is calculated on the basis of additive inverse property.
Additive inverse property states that the sum of a number and its inverse will be zero.
Here, the value of 9x+(-9x) is obtained as zero.
Hence, option (a) is the correct answer.