A method gives a calculation a name, typed inputs and a return type. Call a helper by passing arguments in its declared order. The names in the caller don't choose the destination parameters; their positions do. Parentheses let you finish an expression before passing its value as one argument.
Java passes arguments by value. For a primitive, the helper receives a copy, so assigning to its parameter can't change the caller's variable. The caller must use the returned value when it wants an updated result. Methods can also share a name when their parameter lists differ. This is overloading, and the compiler chooses the matching declaration from the call. Keep helpers small enough that each has one rule you can explain and test.