human
For a given output find the input of a function machine ![A function machine with 4 rectangles in a row, joined by arrows pointing from left to right. The first rectangle on the left is empty and says "input" above it. The next rectangle has "− 1" written inside it, the next rectangle has "✕ 2" written inside it and the final rectangle on the right has "output" written above it and "8" written inside it.]() What is the input of this function machine? \( 15 \)
gpt
Reverses the order of operations but does not apply the inverse operations when finding the input of a function machine