Three-fourths of the yard is covered in grass but 4/5 of the grass has died. how much of the yard has dead grass?

multiply the 2 together:

3/4 x 4/5 = 12/20 = 3/5 has dead grass

the answer is; biodiversity resulting from few ancestors

adaptive radiation occurs when a population is subjected to a large natural environment with spatial ecological variations. the parts of the population in the different ecologies begin to adapt to their local environments. due to non-random mating across the large populations, this causes the different populations from the large population to speciate within their local environments. they, therefore, diverge to different species sharing a common ancestor.