Evaluate :
17.5 × 3 – 21 ÷ 7 – 3 × 12.5

The correct answer is Option 12.

To evaluate the given mathematical expression, we must follow the standard order of operations, often abbreviated as BODMAS / PEMDAS:
1. Brackets / Parentheses
2. Orders / Exponents
3. Division and Multiplication (from left to right)
4. Addition and Subtraction (from left to right)

The given expression is:

$17.5\times 3-21÷7-3\times 12.5$

Step 1: Perform Division
First, calculate the division part, which is $21÷7$:

$21÷7=3$

Substitute this back into the expression:

$17.5\times 3-3-3\times 12.5$

Step 2: Perform Multiplications
Next, calculate the two multiplication operations from left to right:
First multiplication: $17.5\times 3=52.5$
Second multiplication: $3\times 12.5=37.5$

Substitute these values back into the expression:

$52.5-3-37.5$

Step 3: Perform Subtractions
Now, perform the subtractions from left to right:
First: $52.5-3=49.5$
Second: $49.5-37.5=12$

Thus, the final value of the expression is 12.