Apply order of operations: Evaluate 3.5 + 21 × 1.3

Introduction / Context:
This arithmetic item tests the correct use of order of operations with decimals. Multiplication must be performed before addition.

Given Data / Assumptions:

• Expression: 3.5 + 21 × 1.3
• Standard operator precedence applies: multiplication before addition.

Concept / Approach:
Compute the product 21 × 1.3 first, then add 3.5 to the result. Handle decimals carefully to avoid place value mistakes.

Step-by-Step Solution:

Verification / Alternative check:
Think of 1.3 as 13/10. Then 21 × 13/10 = 273/10 = 27.3. Adding 3.5 confirms the total 30.8.

Why Other Options Are Wrong:
7.28 and 6.13 come from mishandling decimals or reversing operations. 72.8 is a misplaced decimal from 7.28 or from adding before multiplying. None of these is correct as an option text because the exact numeric 30.8 is not listed among the numerical options; hence the right choice here is the text None of these.

Common Pitfalls:
Adding 3.5 and 21 first or moving the decimal incorrectly when multiplying by 1.3.

Final Answer:
None of these (since the correct numeric value is 30.8).