How is the first sentence of the excerpt important to the plot?

2(4p+1)/5< = (3+12p)/4 its less than or equal solve it for me an with explanation plz

In the image, layer a is the topmost layer. layer c contains fossils from the precambrian era. layer b contains dinosaur fossils, and layer a contains fossils of mammals. which two statements are supported by this evidence? 1. mammals lived before the precambrian era. 2. dinosaurs and mammals existed in the precambrian era. 3. dinosaurs evolved after precambrian organisms. 4. precambrian organisms evolved after dinosaurs. 5. precambrian organisms were the first life-forms to become fossilized, according to this sample.

How are students who take the writing portion of accuplacer graded?