Average mark for 4 subjects = 75
Total marks for 4 subject = 4×75 =300
300-83-78= 139
Total marks for Mathematics and Science = 139 Mathematica must be 70 to 79
Science 60 to 69
Possible mark for mathematics = 70
Possible mark for science = 69.
Your answer for mathematics and science must be in
70 and 69
71 and 68
72 and 67
.
.
.
.
79 and 60
Hope this helps