Answer:
Total students that failed in both subjects would be 10
Step-by-step explanation:
Students that passed English : 70 - 40 = 30
Students that passed Hindi : 80 - 40 = 40
Total students that passed both subjects 110 (40 + 40 + 30)
120 - 110 = 10 students failed in both subjects
The 30 & 40 come from the students that passed each subject above, then the extra 40 comes from the amount of students that passed both.