How did the vast incan empire address the problems caused by its size
a by devising a number system to count the population be b by dividing its people into self-sufficient territories see c by creating a communication system based on glyphs d by building an advanced system off roads

The answer is (D) by building an advanced system off roads

Explanation:

The Incan Empire is an empire in the 14th-15th century, which encompasses modern-day Peru, Ecuador, Bolivia, Argentina, Chile, and Colombia. The Incan Empire is responsible for many technological innovations unique to its era, especially improvements to its agriculture industry. It is also known for its textiles and architecture. Due to its large size and terrain, the Incan Empire needed to create a good road system that can be used for transportation, trade, military, and religious purposes.,  

the median of the data is 4.

step-by-step explanation:

the median means the middle number of a given number.

to decide which one is the median, arrange in ascending or descending order. but sometimes, you may find two(2) number in the middle, but it's easy, just add them together and divide by 2.

so,   determine the median of the data. 2, 3, 3, 4, 5, 7, 9

it is already arranged, count 3 times forward and 3 backward and the one left is your answer.

2,3,3,4,5,7,9

our answer is 4.

hope this !