Adjectives are describing words (like good, beautiful, or blue) which are usually used with nouns (like person, flower or sky) to change them or give more information about the noun.
There is no specific syllabus for Problem Solving Assessment (CBSE-PSA) Class 9. It will assess on Quantitative Reasoning, Qualitative Reasoning and Language Conventions.
Language Conventions covers uses of Practical English Grammar, Vocabulary and Comprehension reading. Problem Solving Assessment for CBSE Class 9, NCERT Class IX.