ANSWER
PART A: D) 6
PART B: C) all real numbers
Step-by-step explanation
PART A
First we have to apply the distributive property for the -6 in the left term:

Now we have to put all the terms that contain x on the same side. Add 10x on both sides:

Leave just the term with x on the left term: subtract 12 from both sides:

And finally divide both sides by 4:

PART B
The process for this equation is similar. First we apply the distributive property on the right side:

Note that both sides of the equation are the same. This means that any value for c will make this equation true and hence, the solution is all real numbers