R^2 + 4r = 0 please show work

How do i solve uniform motion problems?

In a singing competition, there are 150 participants. at the end of each round, 40% of the participants are eliminated. how many participants are left after n rounds?

Arepresentative from plan 1 wants to use the graph below to sell health plans for his company how might the graph be redrawn to emphasize the difference between the cost per doctor visit for each of the three plans?