in a promotion at a local diner ever twelfth customer will get a free hamburger and every ninth customer will get a free milkshake which customer will be first to get a free sandwich and a free drink

Relax

Respuesta :

The 36th customer

The common denominator between 9 and 12 would be 36

9 th customer -> 18th customer -> 27th customer - > 36 th

12th -> 24th -> 36th