Please help me answer this question

Identify the initial amount a and the growth factor b in the exponential function. a(x)=680*4.3^x

Type the correct answer in the box. use numerals instead of words. if necessary, use / for the fraction bar. a city water tank holds 20 gallons of water. a technician empties 25% of the tank. how many more gallons of water must be removed from thetank so that it has 5 of the water that it started with: the technician must removemore gallons of water for the tank to have 5 of the water that it started with.

The relative growth rate for a certain type of fungi is 60% per hour. a small culture has formed and in just 6 hours the count shows to be 20,273 fungi in the culture. what is the initial number of fungi in the culture?