The chapter is 8pages long. kosta read 1/4 of the chapter aloud. then christina read three pages to the class. how many pages have they red so far.

Number of pages that the chapter has = 8
Number of pages of the chapter that Kosta read = (1/4) * 8
                                                                               = 1 * 2
                                                                               = 2
The number of pages of the chapter read by Christina = 3
Then
The total number of pages of the
chapter read by both of them = 2 + 3
                                                = 5
 So the total number of pages of the chapter that has been read by Kosta and Christina is 5. I hope the procedure is clear enough for you to understand.