One, is growing enough food to make it cheap enough.
Two, is being able to transport the food cheap enough .
Three even if you can transport and grow the food cheaply, you still won't be able to get food to people in war zones.
These problems are solvable.
Currently we have enough food to feed the world, currently we can transport food to them, just it may be expensive. But there are still places that you can't get food to because they are being oppressed.
We all know of how there is enough food for everyone (at the moment). It's just that some people have loads and others have none. There is enough food if we share it out but unfortunately, people do not want to share what they've got, so we are stuck with the same problem.
Humans are selfish, despicable creatures and as long as we roam the planet, people will always be hunger.
This does not apply to everyone, but we are unwilling to share our wealth. We put our needs first, at the expense of others and as long as we keep up our selfish, repulsive ways, there is no solution for hunger.
Although almost everyone wants to abolish hunger, there is always something in the way: greed and the need to put oneself first.