variables addition

hello and thanks by advance.

I 'm trying to gamify a course. At the begining each person is given four types of ressources. For example (apple, beer, cake, carrot) each item cost a price and each user is given a certain number of each element.

Exemple:

Carotts  3$  2 pieces
Apple 2$     4 pieces

During the course the user can earn ou loose some of these items and a score must be calculated.

So i have created for each item three types of variable : numberApple; priceApple; totalApple. plus a total variable.  each time the score is called a table appear from a master slide where are intégrated the références.

The trouble is that and i don't see how i could calculate the score of each item with the trigers. When i want to adjust the variable i'm not allowed to do

applepoints*numbreapple = totalapple

and at the and totalapple+total carotts +   totalbeer+ totalcake = totalgeneral.

 

Thanks by adance Ben rom France