solvable, insolvable, intractable, irresolvable, insoluble, solving, insuperable, vexing, unsolved, surmountable, unresolved, unresolvable, resolvable, knotty, existential, perplexing, unanswerable, simultaneous equations, insurmountable, thorniest, unaddressed, implausible, trivial, incomprehensible, uninteresting, fixable, abstruse, hopeless, unsurmountable, unattainable, nettlesome, unexamined, conquerable, reformable, complicated, unknowable, fathomable, unfathomable, discussable, unreachable, baffling, problematic, unmanageable, inedible, unobtainable, impenetrable, gordian knot, mortal, unavoidable, graspable, inextricable, daunting, impossible, useless, thinkable, unimportant, unmovable, taboo, unnamable, unconceivable, incommensurable, unimaginable, unachieved, sisyphean, infallible, unexplainable, unthinkable, unthought, unsusceptible, irrelevant, plausible, incommunicable, knowable, undecipherable, infinite, unsatisfying, undebatable, sticky, falsifiable, invisible, irrefutable, maladapted, schrodinger equation, undistinguishable, epistemological, unclarified, depthless, unfixed, inconsequential, inscrutable, irreducible, dirichlet, unuttered, definitional, unchangeable, unfathomed, mystifying, puzzling, irreconcilable, contentless, festering, escapable, nontrivial, serious, tractable, analogous, complex

unsoluble