A homework answer gives 4 - 9 - 3 as -2, worked out by taking 9 - 3 first. What is the correct value?

Erklärung

Working from the left, 4 - 9 lands five steps below zero, and taking three more away drops the running total three steps lower still. Grouping the closing pair of terms rewrites the line as 4 - 6, but the second minus sign applies only to the 9 and not to whatever follows it, and adding all three figures instead reports sixteen.