Find the unknown in this equation.
noun, noun which may take the genitive case particle 'no'
unknown quantity; uncertain factor
Figurative use for something whose outcome or nature is not yet known; often used with だ or の before nouns.
Sales of the new product are still an unknown quantity.
His ability is an uncertain factor, but I have high hopes.
His true ability is still an unknown quantity.
Solve for the unknown in this equation.
Whether this plan will succeed is still uncertain.