The answer to your question is knowledge. Scientific knowledge is the information gathered by the systematic study of nature.
The economic system may be production,allocation,distribution,firms,and how the government responds to the economic problem.
$15 by 2.60 times 4.5 is 11.7 and 11.7 plus 3.30 is 15
Tropical climates are characterized by monthly average temperatures of 18 °C (64.4 °F) or higher year-round and feature hot temperatures. Annual precipitation is often abundant in tropical climates, and shows a seasonal rhythm to varying degrees.
Area. Around the equator, from 23.5° further north to 23.5° southern latitude.
Sun path. Sun at the zenith (90°) at least once per year, never lower than 43°
Average temperature. >20 to 30°C.
Minimal temperature. 0°C (no frost)
Maximal temperature. Up to 40°C (seldom more)
