The population of a country is growing exponentially. The population in millions was 120 in 1970 and 150 in 1980.
(a) What is the population t years after 1970?
(b) How long does it take the population to double?
(c) When will the population be 400 million?
The Attempt at a Solution
I don't know how to start the equation, so I listed out the years and the populations to no avail.