how to calculate total in javascript with buttons

Question

Hi folks,


i had one html form to calculate total marks of 3 questions.this form can be seen in attached file.


for every question,we will have two buttons for 0 and 2.
and underneath one text field to display total.


initially, i have pressed 2 button for all questions and total 6 was displayed in total text box.


Task:if i want to give 0 marks to first question.then it will show 4 marks in total text box.but it is adding 0 marks to total 6 marks.
Please let me how to fix it.


Thanks in advance.....


Thanks
Ravi Gaddam