Question

Pam typed 2.5 pages in 15 minutes. At that rate, how many minutes will it take her to type 23 pages?

Answer 1

Well, first of all, you have to compare;
15 minutes=2.5 pages
              x=23 pages
   Then you cross multiply. By the way, i replaced the unknown with x. Anyway, x multiplies 2.5 and 23 multiplies 15. So that will be;
2.5x=345
  Then you divide both sides by 2.5. This is done to remove all that is attached to x to find x
2.5x/2.5 = 345/2.5
  Therefore, 345 divided by 2.5 is 138. So;
x=138
  It will take 138 minutes to type 23 pages. HOPE I HELPED. 

Answer 2

In the given question, it is already mentioned that Pam takes 15 minutes to type 2.5 pages. this information should be used as the main information for reaching the desired answer.
Pam typed 2.5 pages in = 15 minutes
Then time taken by Pam to type 23 pages = (15/2.5) * 23
                                                                     = 345/2.5
                                                                     = 3450/25
                                                                    = 138
So Pam will take 138 minutes to type 23 pages