The independent variable in these equations based on how they are written is x, since y is a function of x here so y depends on the value of x, while x can be changed freely.
So, for each of these questions, plug in the given value of the independent variable for x.
Independent variable equal to 10: 0.1*10 + 5 = 6
Independent variable equal to 50: 0.1*50 + 5 = 10
Independent variable equal to 120: 0.1*120 + 5 = 17