Simple looking equation stumps people - can you remember the 'special rule' to get right answer?

In grade school, you were constantly drilled on mathematics. But as an adult, those lessons all too often fall to the wayside. See if you can remember elementary formulas with this math problem.
CNBC

Household energy costs are expected to rise steeply this winter — here's how you can save

Personal and small business cards issued by U.S. Bank are currently not available on CNBC Select and links have been redirected to our credit card marketplace where you can review offers from other ...