The adjective would be insoluble, unsolvable, or impossible.
"panacea"
Use the equation, speed = distance / time, substitute in the given information from the problem and solve it.
Sportsmanship is a word substitute for spirit of game
A verb meaning to make easier is facilitate.One meaning to make less complex is simplify.
There is no one-word substitute in English for "son-in-law."
A word substitute for the sentence "A fault that can be forgiven" is "venial".
what word can I substitute for constitutes
you can not substitute me. The director Substituted lead actor.
The word you want is florist.
The opposite of a problem (challenge, difficulty) could be a solution, answer, or fix.The opposite of the adjective problem could be easy, facile, or effortless.
By definition, an equation has a solution. The word comes from "equal". Some mathematical problems do not have solutions. For example, 1/0 = X is a problem with no solution. You know, in this example that there is no solution because of the "divide by zero" rule. Most insoluble problems are insoluble because of some rule that keeps you from moving ahead.
The noun 'substitute' is a singular, common noun; a word for someone or something that takes the place of another.The noun 'substitute' is a concrete noun when used for a physical person or thing.example: Soy milk is a good substitute for dairy milk in recipes.The noun 'substitute' is an abstract noun when used for a concept.example: Excuses are no substitute for doing the right thing.The word 'substitute' is also a verb (substitute, substitutes, substituting, substituted).The noun form of the verb to substitute is the gerund, substituting.A related noun form is substitution.