Who is invetor the abacus?

What is the name for a1f3? What geometric term can be used to describe things like F as a mark? Does a cardiac cycle last an average of 30 seconds? How much does gas cost in England? How are percents used and what they mean? Square root of 3600? Is 3T greater than or less than 5999 lb? What is the perimeter of the square in terms of x of the length is 2x-1? What is the importance of measurement in medicine? How do you factorise x squared - x-6? What is the terms use to keeping data for years decades centuries? What is an dihedral on an airplane? 20 wrong out of 100 questions is what grade? What is 30 over 48 in its simplest form? When rolling prints from your left handwhich way do you roll your fingers and thumb? How large is 0.31496063 inches? X to the power of x equals 46'656 what is x? How do you do polynomial inequalities? How much one kilobites per second? What is te answer for 7 x 9?