Using the numbers [28, 27, 12, 6], create an equation that equals 108. You can use basic arithmetic operations (+, -, *, /) and each number can only be used once. Show your work in <think>  </think> tags. And return the final equation and answer in <answer>  </answer> tags, for example <answer> (28 * 3) / 2 + 4 = 20 </answer>.