Answer:
Fraction in simplest form as

Explanation:
Given as,
Fraction of students got A in first period class =

Fraction of students got A in second period class =

Now,
Fraction of more student got A in first period class to second period class =
-

or,

Or,
,
Again covert this fraction in simplest form
simplest form : A fraction is in simplest form, when numerator and denominator can not be any smaller, but still being whole number.
So, this fraction in simplest form as
Answer