Answer:

Step-by-step explanation:
The equation to solve for "a" is:

The first step is to convert all of them to same bases.
9, 81, and 27, all can be expressed in base 3, lets do this:

We can use the property:
to simplify further:

The right side has 2 same bases multiplied, we can simplify this using the property: 
Thus, we have:

Now, both sides have same base, so exponents would be equal. Now lets equate and solve for "a":

So,
a = -4