Some leftover food is good to eat after 7 days.
But it depends on the food and how the leftovers were stored.
If the leftovers were noodles without an meat then the noodles could be okay in the refrigerator for 7 days.
But if the noodles or other leftover food smells bad or tastes bad or has mold on it then throw it out.
Most food lasts around 3 to 5 days in the refrigerator before it goes bad and if the food is meat or has meat in it then the leftovers would go bad within 5 days at most and sometimes sooner.
If you've had the leftover food frozen then the leftovers would always be good to eat after 7 days.
Freezing the leftover food makes the food last longer because the freezer temperatures prevents the bacteria from growing on the food which causes the spoilage.
If the food smells bad, tastes bad or looks bad or has mold on the food then throw it out because it's unsafe to eat.