Answer:
a + b - c - d
Explanation:
The rules of exponents are ...
(x^a)(x^b) = x^(a+b)
(x^a)/(x^b) = x^(a-b)
Using these rules on your expression, we can simplify it to ...
(3^a) · (3^b) ÷ (3^c) ÷ (3^d)
= 3^(a+b) ÷ (3^c) ÷ (3^d)
= 3^(a+b-c) ÷ (3^d)
= 3^(a+b-c-d)
_____
The Order of Operations requires multiplication and division be evaluated left-to-right in order of appearance. The ÷ symbol means the same thing as the / symbol in this context: whatever is on its immediate left is divided by whatever is on its immediate right.