Karen can read 10 pages and complete 15 math problems in 30 minutes.
How long will it take her to do her homework if she has 30 pages to read and 45 math problems to complete?
Karen can read 10 pages and complete 15 math problems in total, so in 30 minutes, she can complete 30/10 = <<30/10=3>>3 sets of 10 pages.
Similarly, she can complete 45/15 = <<45/15=3>>3 sets of 15 math problems in 30 minutes.
Therefore, it will take her 30 minutes x 3 = <<30*3=90>>90 minutes to do her homework. Answer: \boxed{90}.