im not sure what this question means
A bacteria culture starts with 980 bacteria and grows at a rate propotional to its size. After 6 hours there are 5880 bacteria.
Find the population after t hours (function of t)
You must have seen ONE example?! Based on the title of your post, I suspect you already have at least SOME clue how it all will turn out.
If C(t) is the size of the culture at time t,
"grows at a rate propotional to its size" means $\displaystyle \frac{dC(t)}{dt} = k*C(t)$.
You must learn to solve that (It's a separable differential equation.) and use the given conditions to discern the required parameters.