I'm fairly new to statistics and have a project where I investigate if the difference between two variables can predict the value of a third variable. And I am unsure if I should use simple or multiple regression.

The participants in my sample has answered three surveys:

A) Emotions they have had during the week

B) Emotions they ideally want to have

C) Their life satisfaction

My hypothesis is that the difference between the mean score of emotions people report they have (A), and the mean score of the emotions the same people report they ideally want to have (B) can predict the same people's score on life satisfaction (C).

Can I just calculate the mean difference of A and B and use that in a linear regression to see if it predicts the value of C?

Or should I use a multiple regression instead where A and B are predictors of C?

I ask because I don't know if it is a no-go for some reason to just use the raw difference between the two variables in my case.

I hope you can help. Thank you so much!