Let x be the number of correct answers of the questions in a competitive examination, then (120 – x) will be the number of wrong answers of the questions.
Then, by given conditions,
(x×1)−((120−x)×12)=90
⇒ 3x2 - 60 = 90
⇒ 3x2=150∴ x=150×23=50×2=100
Hence, Jayanti answered 100 questions correctly.