This new way of counting included which idea? a decimal system
a calendar system
the concept of pi
the introduction of algebra

The answer is A. A decimal system

Explanation:

plz mark brainiest

for e2020. the answer would be some directions from the mountain range so we can find mt. whitney. to locate which direction is north, you should use a   compass. this would not only find mt. whitney, but also becuase of this long paragraph you would get points because it's not like anyone actually reads your work becuase once they read the first sentence it sounds dumb enough to not read becuase i'm not good at answering this but the answer is compass for your benefit.

for e2020 ; -;