Answer:
50%
Step-by-step explanation:
Girls                       Boys
total: Â Â Â Â Â Â Â Â 59 Â Â Â Â Â Â Â Â Â Â total: Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 41
- Chemistry    35          - Physics              2
            = 24                   =           39
                         - Chemistry ( 30 - 6 )    24
                                  =           15
Total boys and girls for Biology = 35 + 15 = 50
% = 50/100*100
  = 50%