Who inverted the abacus?

How many feet deep do most trenches on excavations accidents happen on? 0 95 0 07? How many sides does a 2D triangle have? What is the rule for multiplying an odd and even number? How many zeroes in 32 million? How many solutions can two lines have that intersect once? What does CAPTCHA error mean? A basket holds n apples You pick 2n-3 apples and your friend picks n plus 4 apples Write an expression that represents the number of apples you and your friend picked Interpret the expression? Definition of independent variable and controlled variable? The meaning of hermeneutics in the Book of Genesis period? What is 0.00062 in word form? Where two sides of a polygon intersect? What 3 consecutive square numbers have a total greater than 50 but less than 100? What is the mean for 22 21 19 19 19? How do you write 14112004 in roman numerals? How do you turn 336 percent into a fraction? How is 32.14 written in scientific notation? How do you write eight and twenty one thousandths? How do you round 0.116 to the nearest hundredth? What is 22.6 in simplest form?