#### Answer

There will be 14,580 rabbits after 3 years.

#### Work Step by Step

As x represents every half-year period, we know that x will equal 6 because there is a three-year time period. 3 years is the same as 6 half years. Therefore, simply plug in 6 for x in the equation:
f(x) = 20(3$^{x}$)
f(6) = 20(3$^{6}$)
f(6) = 20(729)
f(6) = 14,580