Solving exponential equation

In sporting tournaments, teams are eliminated after they lose. The number of teams in the tournament then decreases by half with each round. If there are 16 teams left after 3 rounds, how many teams started out in the tournament?

[list=1] [*]Read and reread the scenario to identify the known and unknown quantities. [*]Create expressions and equations from the known quantities and variable(s). [*]Substitute the values into the general form of the equation [math]y = ab^x[/math]. [*]Follow the order of operations to solve the problem. [*]Interpret the solution in terms of the context of the problem. [/list]