There are 7 trout fish in a pond, and the population doubles every year. find the population after t years.

We can find the equation for this by multiplying all of the values given. We can do this because, since we want to find the number of trout in t years, we obviously multiply 7 by t. That gives us 7t. We also multiply 7t by 2 because the population doubles every year, hence to find the population in t years, we also need to multiply by two. That means the expression for this situation is 14t 

If your looking for the equation it would be something like 7(2t)= x and x= the population