Please help.
Carbon-14 has a half-life of 5,730 years. A plant fossil was found to contain 1.75 grams of carbon-14. How long ago did the bone contain 7 grams of carbon-14?

What is the independent variable in this investigation? mass volume sample number substance density

Nebulae are enormous clouds in outer space. they are made mostly of hydrogen gas, helium gas, and dust. some nebulae glow brightly, while others do not. the stars that people see are huge, bright balls of glowing gas. they are made mostly of hydrogen and helium. which statement correctly describes other ways in which nebulae and stars are different? a. stars can form inside a nebula but a nebula can never be produced by any star. b. a star always has a higher density than a nebula. c. stars can never form inside a nebula but a nebula can be produced by any star. d. a nebula always has a higher density than a star.

How many molecules are in 6.0 moles of methane