Using the numbers [67, 34, 21, 10], create an equation that equals 448. 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> ((1 + 2) * 3) / 4 = 5 </answer>.