87.5% of those who passed the first test also passed the second test.
Lets assume, the total number of students in the class = X
As 80% of the class passed the first test, so the number of students passed the first test = 80% of X
[tex]= \frac{80}{100}* X\\ \\ = 0.8X [/tex]
and the number of students passed both tests
= 70% of X
[tex]= \frac{70}{100} * X\\ \\ = 0.7X [/tex]
It means, this 0.7X of those who passed the first test also passed the second test.
So, the percentage of 0.7X in respect of 0.8X is :
[tex] \frac{0.7X}{0.8X} *100 \\ \\ = 0.875 *100 \\ \\ = 87.5% [/tex]
Thus, 87.5% of those who passed the first test also passed the second test.
