Institution: জগন্নাথ বিশ্ববিদ্যালয় Exam: C ইউনিট : 2017-2018
Topic: Arithmetic Mathematics (পাটিগণিত), Subject: Mathematics (সাধারণ গণিত)

Best Answer Explained in Below-:

To solve the question "80 টাকার তিন - চতুর্থাংশ এক- দশমাংশের অর্ধেক ক তার?" we first need to break down the components step by step.

1. **Understanding the components**:
- "80 টাকার তিন-চতুর্থাংশ" refers to three-quarters of 80.
- To calculate three-quarters of 80:
\[
\text{Three-quarters of } 80 = \frac{3}{4} \times 80 = 60
\]

2. **Finding one-tenth**:
- Next, we need to find "এক-দশমাংশ" or one-tenth of 60, which we just calculated:
\[
\text{One-tenth of } 60 = \frac{1}{10} \times 60 = 6
\]

3. **Finding the half**:
- Finally, we need to take half of this one-tenth value:
\[
\text{Half of } 6 = \frac{1}{2} \times 6 = 3
\]

After calculating all parts, we find that the final result is 3. Therefore, the correct answer to the question is **B) 3**. This logical progression of breaking down the question into manageable parts allows us to navigate through the calculations effectively to arrive at the correct answer.