What is 3 x 4 + 37- 21x 10? im just playn get these points

The information box says that the han added 4,000 miles of wall.refer to the mileage scale.how can this be true?

23. how does specialization among nations encourage interdependence? nations work together to share labor and resources to produce vital goods. nations sign treaties prohibiting taxes on imports. nations produce specific goods and then trade to obtain things they need. nations that are more developed agree to fund development in nations with limited industry.

The edict of nantes states a: protestantism was to be the official religion in france b: huguenots would rules france and allow catholics to practice freely. c: catholicism was to be the official religion in france but protestants could worship freely. d: catholicism was to be the official religion in france and protestantism was to be outlawed.