How to get data from inputs?

[fearlay]

Hello,

First of all, I want to warn you about my english - I'm not native.

I want to create a really simple app for Windows. It may look like this:
uQ41UYs.png

First two inputs are QDoubleSpinBox types
Third input is QLineEdit type.
and finally, the Result is a QLabel

All I want to do is simply add/multiply NUMBER_1 by NUMBER_3. The Result has to be changing dynamically.

How to get data from those inputs? And then how to put this data into QLabel (Result)?

Any ideas?

Thanks.