The Collaborative International Dictionary of English v.0.48:

Solvable \Solv"a*ble\, a. [F. solvable. See Solve, and cf.
   Soluble, Solvible.]
   1. Susceptible of being solved, resolved, or explained;
      admitting of solution.
      [1913 Webster]

   2. Capable of being paid and discharged; as, solvable
      obligations. --Tooke.
      [1913 Webster]

   3. Able to pay one's debts; solvent. [Obs.] --Fuller.
      [1913 Webster]

WordNet (r) 3.0 (2006):

solvable
    adj 1: capable of being solved; "such problems are perfectly
           solvable" [syn: solvable, resolvable]