Fraction A comes from the original substitution of the numbers and units into the solved equation. Fraction B shows the inversion of the fractional unit into the numerator. This is a really useful way to simplify fractions that seem complex. Fraction C shows the same fractional unit integrated into the whole fraction and cancels the unit of gram. Step C is not needed if you want to cancel the gram unit in the numerator. Fraction D shows what happens when you cancel a unit without its metric prefix. The k is just one thousand now, so k (cc) is the same as one thousand times cc which is a liter. Fraction E shows the final unit. Many students make math mistakes by failing to simplify fractions in the denominator.