It is hard to tell what that is supposed to be without more parentheses. My first guess was that you meant

(2^x+ 2^(x-1))/(2^x+ 2^(x-1)) but that is equal to1because the numerator and denominator are the same.

But then by the third step that "-1" in the denominator has mysteriously become "+1". Did you intend

(2^x+ 2^(x-1))/(2^x+ 2^(x+1))?

In any case, if the problem is either of those, you can't use a "multiplication rule" because you don't have a multiplication.

It is true that (2^a)(2^b)= 2^(a+b) but you have 2^a+2^b, the sum, not the product.

If it really is [tex]\frac{2^x+ 2^{x-1}}{2^x+ 2^{x+1}}[tex], I recommend you factor out of the numerator and out of the denominator. That will give

Simplify that.