In greenville, one in every eight houses has three computers

The complete question was

Write a ratio in three ways In Greenville, about one in every eight homes has three computers.

A) 1 to 3, 1:3, 1/3
B) 3 to 8, 3:8, 3/8
C) 1 to 8, 1:8, 1/8
D) 8 to 11, 8:11, 8/11

And the problem also tells you that you needed to compare the first quantity with the second.

So, ONE in every EIGHT means 1/8, 1 to 8 or 1:8 which is option C.

The method to find the female dormitory is 2-d=800