Are you Smarter than a Fourth Grader?

A co-worker in my department has a son in the fourth grade who gets these weekly math challenges. I must say for a fourth grader are pretty hard. Usually they are solved with algebra (which they have not learned yet) but the kids are challenged to try to figure it out anyway they can graphs, guessing, pictures etc...Now my co-worker gives these word problems to several of us in the department to work out. Usually it takes me a few minutes to kick out my basic algebra skills and figure it out.

The first time we did it, my co-worker couldn't solve it herself but insisted that my answer had to be wrong because I did it too fast because apparently the rest of my department took over a half hour to solve it (their answers were wrong by the way).

The second time I was critiqued for not showing all of my work . We have yet to do one where I haven't had to explain how to get the correct answer to at least one person.

I know I sound really bitchy and condescending. I fully acknowledge that not everyone is good at math and I'm totally okay with that there are lots of things I can't remember from school. The thing is all of these people work in my department - the ACCOUNTING DEPARTMENT!!! They are paid to work with numbers all day and should not look at me oddly because I remember how to do simple algebra!!!

So here's the problem. Feel free to post your answers in the comments.

A magic money box doubles any money put into it and then adds $1. Kara put some money in the box and the box did its magic. She then took this new amount of money and put it back in the box again. After the box did its magic again, Kara took of $31. How much money did Kara originally put into the magic money box?