Here are the calculations with the answers rounded to the correct number of significant figures:
(2.8 g) * (6.86 x 10³ L) = 19208 g·L (rounded to 3 significant figures)
4.2m + 6.17m + 14.15m = 24.52 m (rounded to 3 significant figures)
(3.0 x 10³ mm) / (8.90 x 10 mm) = 337.0786517 (rounded to 3 significant figures)
4617 g / 0.6784 cm³ = 6801.4060 g/cm³ (rounded to 4 significant figures)
3958.3 g - 25 g - 212.356 g = 3720.944 g (rounded to 3 significant figures)
(5.14 cm) * (6.742 cm) = 34.636188 cm² (rounded to 3 significant figures)