Using the numbers [1, 3, 40, 30], create an equation that equals 120. You can use basic arithmetic operations (+, -, *, /) and each number can only be used once. Show your step-by-step work in <think> </think> tags. And return the final equation and answer in <answer> </answer> tags, for example <answer> (1 * (3 + 40)) * 3 = 120 </answer>.