Using the numbers [23, 78, 40, 17], create an equation that equals 147. You can use basic arithmetic operations (+, -, *, /) and each number can only be used once. Make sure to show your work in <think> </think> tags. And return the final equation and answer in <answer> </answer> tags, for example <answer> (23 + 78) * 40 - 17 = 147 </answer>.