Solve world hunger?

Okay.

Distribute food stamps valued highly enough to pay for a healthy amount of varied food to every single person on Earth, regardless of income, country, or anything else. You can buy more food on top of that if you want, of course. Ban protectionist measures such as tariffs and local subsidies (global subsidies may be okay, but local ones are by definition protectionist and bad). Invest into genetics research to develop better crops of greater hardiness and nutritional value with higher yields. The last is not necessary in the short term, we have plenty of food for everyone today, but it'll be good preparation for the future.