Hi student,

Best of four means the four subjects in which you scored the highest. Then take a percentage of the marks obtained in those four subjects out of 75 and that would be your final score. Since the total in punjab board of each subject is 75, you would have to take a percentage out of 75 marks. Out of those four subjects language is compulsory. You could choose any 3 core subjects from the rest. To take out the percentage:

[(Total score in all four subjects out of 75) *100]/(75*4)