Hi,

We appreciate you for being part of Windows 10.

This issue may arise if you are using Standard calculator.

Try the below steps:

Open the Calculator through Start menu. Once you open, click on menu button (Three horizontal lines at top left corner). Select Scientific calculator. Now type 1+2*3, it will give the answer as 7.

Note: There will be different way of operations integrated into Standard and Scientific calculators.

Hope the above information helps. Kindly let us know if you need any further assistance with Windows. We are glad to assist you.

Thank you.