1. The problem is to solve or understand typical one-mark questions from 9th NCERT Mathematics. 2. These questions usually test basic concepts like algebraic identities, linear equations, polynomials, coordinate geometry, etc. 3. For example, a common question might be: Find the value of $x$ if $2x + 3 = 7$. 4. The formula or method used here is to isolate $x$ by performing inverse operations. 5. Step-by-step solution: 1. Start with the equation: $2x + 3 = 7$ 2. Subtract 3 from both sides: $2x = 7 - 3$ 3. Simplify the right side: $2x = 4$ 4. Divide both sides by 2: $x = \frac{4}{2}$ 5. Simplify the fraction: $x = 2$ 6. This shows the value of $x$ is 2. 7. Another example: Find the value of $(a+b)^2$ using algebraic identities. 8. The identity is: $(a+b)^2 = a^2 + 2ab + b^2$ 9. This helps quickly expand squares of binomials. 10. These one-mark questions test quick recall and application of such formulas. 11. Always remember to perform operations equally on both sides of an equation. 12. Practice these basic steps to build a strong foundation in algebra and coordinate geometry. Final answer depends on the specific question, but the approach remains consistent.