How did the location and environment of the Aztec help them conquer an empire?

The geography of where the city was located helped them because it was an aquatic environment that provided protection because it was surrounded by a huge lake. This process created extremely fertile land to plant and even assisted in the population growth of the city of Tenochtitlan. The climate in this region of the Aztec Empire was very hot and humid. The Aztecs kept their city clean by keeping the canals full of fresh water which came from the mountain springs.  In periods of low rain and water, the city of Tenochtitlan would ask neighboring city states to open their canals and let the fresh water flow down.  This was dangerous, as the Aztecs learned one season.  These canals and lake systems were unpredictable and in one instance, the water kept rising in the city and they had to evacuate.  Since the Aztecs lived on an island in the middle of Lake Texcoco, they had to build causeways to get from the island onto dry land.  The designers of the city created three main causeways which were the entrances that led to the center of the city. The Aztec Empire had a great many resources and the people were able to farm many crops.  The valley rivers in the region allowed for fish, shrimp, and a pasta that occurred naturally called ahuatle.  Nature’s abundance reached from the Pacific Ocean to the Gulf of Mexico where they could find crabs, oysters, and fish.  The land provided rabbits, snakes, deer, and wild turkey.  Within the city, they were able to grow many crops with the formation of the chinampas such as cocoa, vanilla, bananas, squash, pumpkin, beans, chili, tobacco, onions, red tomatoes, green tomatoes, sweet potatoes, jicama, huautli and maize.  

Explanation:

what is the tax base for the sales tax?

it should be (usually ) 6%