Why am I getting this error?

[Tamer_Muhassil]

It is not possible to process the number 150 that I wrote in a separate TextBox.

[Taifun]

This

gives you a component...which looks like this

@Tamer_Muhassil

com.google.appinventor.components.runtime.TextBox@ec39260

remember, you have components in that list,... so if you want to get the text of that textbox component, use the get text block from the advanced textbox drawer together with that select list item block

Taifun

[Tamer_Muhassil]

It Sees It As Text.
Even If I Multiply It By 1, It Still Sees It As Text. Same Error

[ABG]

Are you French?

AI2 needs decimal points, not commas in its numbers

[Tamer_Muhassil]

I thought the opposite and replaced the Dots with Commas.
The problem was that I didn't select text from the drawer.
Thank you very much to all of you.
Merci beaucoup à vous tous
I am not French.