Using the numbers [6, 77, 73, 20], create an equation that equals 20. You can use basic arithmetic operations (+, -, *, /) and each number can only be used once. Show your work in <think> </think> tags. Assume that 77 and 73 cannot be used until a higher value is reached. Show the complete and final equation with the target shown in the prompt in <answer> </answer> tags, for example <answer> (1 + 2) / 3 = 1 </answer>.
