Question 251978
Let x=initial number of students
Number of females=(7/11)x
Number of males=(4/11)x
If 3 females are absent tomorrow, we will have (7/11)x-3 females remaining
If 12 males are absent tomorrow, we will have (4/11)x-12 males remaining
so, (7/11)x-3=(5/7)(x-15) and/or (BOTH SHOULD GIVE THE SAME ANSWER)
(4/11)x-12=(2/7)(x-15)
Multiply the first equation by 77
49x-231=55x-825  subtract 55x from and add 231 to each side
49x-55x=-825+231
-6x=-594
x=99---number of students in the initial class
x-15=99-15=84  #students in class tomorrow--------------------ANSWER

Hope this helps---ptaylor