xsqrt(3)/2
When you say "K(square root of 3) divided by 2" is the equation above what you mean, if x is substituted for K? If so, then you should remember that area (K) is equal to 1/2(base)(height), and you are given the height, which is 12. That leaves two variables, K, which we what to find, and then the base of the triangle. Because it is an equilateral triangle, we know that the height and the base are related: multiply half of the base by square root of 3. Oh wait! That's already given to us in the problem! Just set xsqrt(3)/2 = 12 and solve.
This is my best guess at the solution. I is my first time working with math via the computer, so I might have misinterpreted the information, but i hope it helps