Something resolvable can be figured out or settled on. In other words, it has a solution. If a dispute between two countries is resolvable, that means it's possible for them to come to an agreement.
An ongoing argument with your incredibly messy sister might seem impossible to settle if you share a bedroom. Keep negotiating and it may be resolvable — maybe you can hang a curtain and divide the room in half! We get resolvable from resolve and its Latin root resolvere, "to loosen, relax, set free, or make void."