I need to explain why this program works

[STEMON]

I'm not sure if this is the right group to post to, but I need help and am relatively new to App Inventor.
I recently made an app in which the price and quantity of two products (A & B) are typed into fields and it's supposed say which product is cheaper or if they're both the same amount. When nothing is entered, or if zero is entered in specific places, the message is supposed to be displayed.

I made this program in which the list is equal to "nothing" and "0" in the text, but this message comes up for both, respectively.

When I change the list not equal to it works and the message is displayed. I need to be able to explain why this is.

Can anyone help me out please? Thanks! Please remember I'm an beginner!

[Ramon]

You are comparing a list with a single value, which is wrong.

as you can see, with the equal to comparison, the result is false so, it will try to do the division and it will fail.

With the not equal to comparison, the result will be true and it will enter in the if statement, with no divisions.

If you want to check if the textBoxes are not empty (or wit 0 value) you need to check each item, You can try something like this: