You cross two unicorns, one that is Rr / Ss with an individual that is rr/ss. The resulting progeny are in the following proportions: 7 Rr/Ss, 35 Rr/ss, 32 rr/Ss, 6 rr/ss. If you wanted to test whether these two loci were independently assorting, what would be the number of expected genotypes to compare your observed to?

The number of expected genotypes to compare the observation to would be 20 RrSs, 20 Rrss, 20 rrSs and 20 rrss

Crossing RrSs with rrss will yield offspring with the following phenotype according to the attached Punnet's square:

4RrSs

4Rrss

4rrSs

4rrss

Total offspring = 7+35+32+6 =

Thus instead of 7:35:32:6, it will be 1:1:1:1 if the two loci were independently assorting. The number of expected genotypes would be 20 RrSs, 20 Rrss, 20 rrSs and 20 rrss

More on independent assortment can be found here:

relative dating involves things like higher layers are most recent than rocks lower in the sequence. this can be extended to the known sequence of fossils. rocks containing rabbit fossils are later than those containing dinosaur fossils.  

absolute dating methods mainly use radioactive elements that have known rates of decay and produce recognizable products. for example potassium 40 decays to produce argon. once a rock has solidified the argon is trapped. by measuring the argon and potassium0 you can get an accurate number for the age.  

some other methods are good for archaeological ages. dendrochronology involves recognizing the sequence of tree rings. the orientation of magnetized particles in baked clay can be used to date a fire.

hope this .. .