Question

Dr. Drange has a collection of 90 books. Of the books, 2/9 are math books, 1/6 are science books, and the rest are romance novels. How many romance novels does he have?

Answer 1

So whenever a question says "of" multiply. So 2/9x90= 180/9= 20. 1/6x90= 90/6= 15. 90-(20+15)=90-35=55.

55 of the books are romance novels. (or 11/18)

Hope this helps!

Answer 2

Solving:

*Math books

$\frac{2}{9} * 90 = \frac{180}{9} = 20\:math\:books$

**Science books

$\frac{1}{6} } * 90 = \frac{90}{6} = 15\:science\:books$

***romance novels (books)

If we have a total of 90 books, being 20 books of mathematics and 15 of science, therefore the amount of books that are missing are novels of romance, soon:

Math + Science + Romance novels = 90 books

20 + 15 + Romance novels = 90
35 + Romance novels = 90
Romance novels = 90 - 35
Romance novels = 55

Answer:
55 books