Ionic 5 for Beginners : using ion-input buttons in ionic5, Input from user

In this video i will show you how to take input from user and how to process it

[konam]

how do I read the input of the user then multiply it by a number already in my code.
for example

the user input 5. Then I have a=2
product = input * a;

then I want to display the output on the screen.

Thank you for your answer.