I need help with this one ASAP I appreciate it , thank you

Find the sum of the first 8 terms of the following sequence. round to the nearest hundredth if necessary.

Samantha swam upstream for some distance in one hour. she then swam downstream the same river for the same distance in only 12 minutes. if the river flows at 4 mph, how fast can samantha swim in still water?

Acertain population of bacteria demonstrates exponential growth doubles in size every 4 days. how long will it take the population to triple in size?