Question 390815
Let # of questions be "x".
----
mark missed 1/5 of the questions on the test.
missed: (1/5)x
---
he corrected 3/4 of the questions he missed.
still missed: (1/4)(1/5)x = (1/20) x
-----
what fraction of the questions did he miss?
1/20 
============
Cheers,
stan H.