Question

Aria´s height is 3 inches less than her brother´s height. her brother´s height is unknown.

Answer 1

We can not find the answer unless we have the height of the brother.

Answer 2

The answer is x-3. We don't know the brother's height, so we make it into a variable. You may pick any variable, but x is a common choice. We then subtract 3 from x, which would give us Aria's height. Since we don't know the height of the brother, we won't know Aria's height.