A mathematics book has 360 pages, of which 50% are on ALgebra, 20% on Geometry and the remainder on Arithmetic. How many pages of arithmetic are there in the book?

50 % + 20% = 70%

then
100% - 70% = 30%
so
0.30 * 360

A mathematics book has 360 pages, of which 50% are on ALgebra, 20% on Geometry and the remainder on Arithmetic. How many pages of arithmetic are there in the book?

I'm seeing that the answer is 108 pages but I can't understand how to arrive at that answer.

Look at what Damon did.

.3 * 360 = ?

To find the number of pages on Arithmetic in the book, we first need to determine the pages dedicated to Algebra and Geometry.

1. Determine the number of pages for Algebra:
The book has 360 pages, and 50% of the book is dedicated to Algebra.
So, the number of pages for Algebra = 50% of 360 = 0.50 * 360 = 180 pages.

2. Determine the number of pages for Geometry:
The book has 360 pages, and 20% of the book is dedicated to Geometry.
So, the number of pages for Geometry = 20% of 360 = 0.20 * 360 = 72 pages.

Now, to find the number of pages for Arithmetic, we subtract the pages allocated for Algebra and Geometry from the total number of pages in the book.

Pages for Arithmetic = Total pages - Pages for Algebra - Pages for Geometry
Pages for Arithmetic = 360 - 180 - 72
Pages for Arithmetic = 108 pages

Therefore, there are 108 pages of Arithmetic in the book.