An actor gains 20pounds for a part and then losses 15 pounds during the filming of the movie to go along with the story. who do you write a addition expression to describe this situation

Let the actor's initial weight be 'x'

He is then gaining 20 pounds. The clue is in the word 'gaining' as it means 'increasing' or in Mathematics can be related as 'plus'

The expression is: x+20

He then loses 15 pounds. The clue is in the word 'losses' as it means 15 pounds is to be subtracted from the last value

Last value is x + 20
The weight now is x + 20 - 15 = x + 5