Question

What is the value of x?
Statement I: x+y=20
Statement II: y=8

• A. Statement I alone is sufficient
• B. Statement II alone is sufficient
• C. Both statements together are sufficient
• D. Neither statement is sufficient

Hint:

In Data Sufficiency, do not spend extra time fully solving the equations once you establish that a unique solution is mathematically guaranteed.
As soon as you see two independent linear equations for two variables, you can confidently conclude they are sufficient together.

Answer 1

The Correct Option is C

Step 1: Note the goal.
We want one fixed value of $x$. We must test each statement on its own first.

Step 2: Try Statement I alone.
It says $x + y = 20$. This has two unknowns, so $x$ could be many things depending on $y$. Not enough by itself.

Step 3: Try Statement II alone.
It says $y = 8$. This tells us nothing about $x$ on its own. Not enough by itself.

Step 4: Combine both statements.
Put $y = 8$ into $x + y = 20$. \[ x + 8 = 20 \]

Step 5: Solve for x.
Subtract $8$, so $x = 12$, a single clear value.

Step 6: Decide sufficiency.
Neither alone worked, but together they give one answer.

Step 7: State the answer.
Both statements together are sufficient. \[ \boxed{\text{Both statements together are sufficient}} \]