It's because of the "&" in front of
internal_organ_cream
- remove them both and it will work:
int internal_organ_cream = 5;
int liquid_organs = 7;
internal_organ_cream = liquid_organs;
When you put "&" in front of a variable name, it returns the address of the variable, rather than it's content - but that will be explained later when you get to pointers. For the moment, just don't use them at all!