At the core of biology and other sciences lies a problem-solving approach called the scientific method. 1  Make an observation. 2  Ask a question. 3  Form a hypothesis, or testable explanation. 4  Make a prediction based on the hypothesis.  Test the prediction.
Xi. Xi is the 14th letter of the Greek alphabet. It is pronounced in Modern Greek, and generally or in English. In the system of Greek numerals, it has a value of 60. Xi was derived from the Phoenician letter samekh. Xi is not to be confused with the letter chi, which gave its form to the Latin letter X.
A smaller number in front of a bigger number means subtraction, all else means addition. For example, IX means 9, XI means 11. You would not put more than 1 smaller number in front of a bigger number to subtract. For example, IIX would not mean 8. You should separate ones, tens, hundreds, and thousands as separate items. That means that 99 is XCIX, 90 + 9, however never should be written as IC.