Duke probably wants you to take the SAT exam. A 29 on the ACT is roughly equivalent to a 1920 on the SATs. About 75% of those admitted to Duke have higher scores than you.

The same is probably true of your GPA. But most of those with lower GPAs probably took AP classes and honors classes. 90% of those admitted are in the top 10% of their High School classes.

You probably exceed the minimum standards that Duke looks for — but unless there is something that really makes you stand out — I think it is less likely that you will get into Duke than it is that you will get in.

Make sure you write a killer entrance essay. It may be the deciding factor.