Which ideas about functions are the most helpful​

It helps in calculating the price of groceries such as fruits.
Step-by-step explanation:
Remember, functions are mathematical expressions that represent or shows the relationship between one or more variables.
For example, let's say a young girl wants to shop for 20 oranges in a mall. If we express the price using the function where;
y represents the total cost of the oranges,
20 represents the number of oranges,
x represents the cost per orange (assumed to $0.99)
Then, by means of the knowledge of function, the girl determines the total cost she to be $19.8 (20*0.99).

Yes you are correct