Answer:
Grades are the depenant variable while hours spent playing videogames is the independant variable.
Step-by-step explanation:
Image result for independent variable
Independent variables (IV): These are the factors or conditions that you manipulate in an experiment. (Hours spent playing) Your hypothesis is that this variable causes a direct effect on the dependent variable. Dependent variables (DV): These are the factor that you observe or measure. (Frades at school)