A simple-looking arithmetic problem can create a surprisingly lively discussion. The challenge is 170 − 30 × 0 + 8 = ? The numbers are easy, but the order in which you calculate them matters.
The correct answer is 178
First, multiply 30 by 0. That gives 0. The expression now becomes 170 − 0 + 8. Work from left to right to get 178.
Why some answers are wrong
One common mistake is to subtract 30 from 170 before handling the multiplication. But standard order of operations requires multiplication before addition and subtraction. You cannot simply work from left to right across every symbol without accounting for that priority.
Here are the steps:
- 30 × 0 = 0
- 170 − 0 = 170
- 170 + 8 = 178
The multiplication-by-zero detail makes this puzzle especially useful as a quick refresher. A zero product does not erase the entire expression; it only makes that particular product zero.
If your answer was 178, you got it. Try sharing the equation without its solution and see who remembers the order of operations.


