You are trying to find height. I am assuming this is a rectangle you are computing, so I will use
Base • Height = Area
(27) • Height = 256.5 // Plugging in what we know
As per Algebra, you have to be able to manipulate terms in an equation in order to find an answer. In reality, it’s right there, just not in a visible form. To do that, go ahead and divide both sides of the equation by 27; this gets rid of the 27, leaving Height, what we want, alone.
(27/27) • Height = 256.5/27 // Division Property of equality
Height = 9.5 cm