The heaviest elements found on Earth were created in stellar explosions (supernovae). Assuming that all the uranium now found on Earth was created in a single supernova and that uranium-235 and uranium-238 were created in equal amounts, estimate the time since explosion occurred given the following data:
Observed relative abundance of Uranium-235 = 0.7%
Observed relative abundance of Uranium-238 = 99.3%
Mean lifetime of uranium-235 = 1.01 x 10^9 years
Mean lifetime of uranium-238 = 6.49 x 10^9 years
I dont know how to start off, any help will be greatly appreciated
Thanks!