 So the error here is invalid operand, variable and variable in operator plus. This means that you're trying to add two different variables that are not of the same type. In this case, we have an integer here, which is 15, a number, and we have a string, which is nix. Since we're trying to add a number to a string, the program doesn't really know exactly what to do. So a way to fix this is to check if the two variables that you're adding are strings, or in the case that instead of a string here, maybe you have a number, but it is still a string. You can always transform any string to int. That way we'll check this string and transform it to 45. So whenever we run it again, we're here 60, which is the result. Or the other way around that could be that you want to have this as two variables. This is very common if you want to do, kind of like printing the value of something, and you have a number that is an integer. You can always transform it to string, and that will show you those two. This happens with a lot of variables, so always make sure that the type of both of the variables that you're trying to add or subtract or whatever you want to do are of the same kind. This is an extra, and maybe you are doing this because you want to show a lot of variables, but you can use the print function with extra arguments. So in this case, you could do, instead of adding them up like this, you can do town, then population. And when I press play, the print function will automatically transform everything to strings and display it to you together. So in this case, it's the same that we had before. This is very useful for debugging. So if you have a lot of different functions that you want to check, you can add them together like so. If you have a variable that changes a lot and you're not sure what kind of type it is, you can always use conditional and type off. And here, a variable, in this case, population. And here you can search on the global scope. We have all the variables that are available to you globally. So you have nil, bool, int, string, whatever you need. In this case, we need the int, which you can use either the number or this all caps variable. So if it's type int, we can print yes. So we know that this happens. You can add this kind of check before any of your operations to make sure that your dynamic variable is of the type that you need.