The question is:

According to the book the answer is 15/6 but the answer i got is 15/2In a section of a city the ratio of private homes to apartment house dwellings is 5:3 . If all the apartment house dwellings are brick structures and 1/10 of private homes are wooden structures , what is the maximum portion of houses that may be brick..

Here is how i attempted it

private homes/apartments = 5/3

since 1/10 of private homes is wooden so 9/10 must be brick.

so total brick structures are

3+(9/10)(5)= 15/2

Am i correct and thats a typo in the book or am i missing something