No one does linear regression (method of least squares) by hand. Instead they utilize some kind of technology. Most commonly, a graphing calculator or Excel is used.
- Handout: Linear Regression in Excel
- How Do I Do Linear Regression in Google Sheets?
- Handout: Linear Regression TI Graphing Calculator
- How Do I Do Linear Regression in Desmos?
Another option is to use WolframAlpha. This is covered in this FAQ.
Each technique should give the exact same answer provided you input the data correctly.