If you could solve any problem in the world, what would it be?

Eliminate usury, fiat currency, partial-reserve "banking", and the abomination of mankind's slavery to the Money Cartel.

In short, replace the evil and immoral money token system with a "currency" based upon time investment. A "time currency". No rich or poor, each as valuable as is their time. And no one could amass or use more time than that which they have as everyone has only a finite amount of time on earth. And no one would receive more time than that which they themselves have invested...

Now the shylocks of the world would be powerless, and everyone would have only that which they have invested of themselves in their fellow man...

I would make sure everyone had enough, enough food, enough clothing, enough shelter, enough jobs.