7a + (4+5a) = 12a+4

use properties and justify each step

7a + (4+5a) = 12a+4

The first step to this is to simplify both sides of the equation.

You have to combine all of the like terms first ...

(7x + 5x) + (4) = 12x + 4

12x + 4 = 12x + 4

Now the second step is to subtract 12x from both sides ...

12x + 4 = 12x + 4

-12x - 12x

4 = 4

Now you will subtract four from both sides and get ...

0=0