So to do that, you need to create one characteristic called "number of persons" with values from 1 to 10 for example.
Then, you create three products, one for adult, one for senior and one for children, and you add that characteristic to each of these products.
Then, you add these three products as options of the product where you want to be able to select the number of child/senior/adult.
In each of these product options, you can click on the "manage variants" button in order to configure the price for each amount of person of that type.