Answer: -5
Explanation:
You have to find a. Here's some steps you can take.
1.) Subtract 12 on the left side of the equal sign to get -6a by itself. When subtracting 12 you must subtract 12 from 42 as well.
2.) Your new equation would be -6a = 30
3.) Now you need to get a by itself. How do we do that? By dividing -6a by -6. REMEMBER: You must also do the same to the right side of the equal sign which is 30 (30/-6)
4.) Your problem should end up looking like this: a = -5