Answer:
Step-by-step explanation:
If 70% passed both, then that means 30% passed either one test, or neither test.
Since 80% passed the first test, we know that 20% of the students failed the first test.
This means that the other 10% of the students came from the 80% that already passed the first test.
These make up 10/80 = 12.5% of the people that passed the first test, meaning your answer is 100-12.5=87.5%
