What is the letter a? 6a+14=-7-a. a=?

6a+14=-7-a

you simplify the equation to the form, which is simple to understand
6a+14=-7-a

you move all terms containing a to the left and all other terms to the right.
+6a+1a=-7-14

you need to simplify left and right side of the equation.
+7a=-21

you divide both sides of the equation by 7 to get a.
a=-3

I would say the answer is -3

All you have to do is multiply