Two trains leave the same station at the same time, but are headed in opposite directions. one train travels at 70 mph and the other train travels at 80 mph. how much times passes until the trains are 600 mi apart?

How do i do this? i don’t understand

Ascientist has discovered an organism that produces five offspring exactly one hour after its own birth, and then goes on to live for one week without producing any additional offspring. each replicated organism also replicates at the same rate. at hour one, there is one organism. at hour two, there are five more organisms. how many total organisms are there at hour seven? 2,801 19,531 19,607 97.655

How do you determine if an ordered pair is a solution to a given equation?