Naturally occurring uranium is composed of three major isotopes, uranium-238 (99.28% natural abundance), uranium-235 (0.71%), and uranium-234 (0.0054%). All three isotopes are radioactive, creating radioisotopes, with the most abundant and stable being uranium-238 with a half-life of 4.4683×109 years (close to the age of the Earth), uranium-235 with a half-life of 7.038×108 years, and uranium-234 with a half-life of 2.48×105 years.
1/ Can we assume there was no preference to form any particular isotope? - leading to the conclusion that the isotopes were originally present in equal proportion?
Can we remember how to use the half-life to get the date of formation based on the assumption made in 1/ ?
The second isotope should give a check on the validity of the assumption made in 1/ .. so all we need is some maths.