This statement is incorrect.
In f(3x), the input 'x' is multiplied by 3 prior to being substituted into the function.
Conversely, with 3f(x), the result (output) is multiplied by 3 after you have calculated the output from the input value.
The correct answers are 0, 5, and 8. Clearly, having negative bags isn't feasible. Additionally, 10 is not possible since the balloon has a weight limit.