I am the number of red tiles in a design with red and blue tiles. The red tiles each have 3 sides. The blue tiles each have 5 sides. There are 3 blue tiles. There are 30sides on the tiles in all. What number am I?

If each blue tile has 5 sides and you know you have 3 blue tiles you can multiply 5 by 3

5 x 3 = 15 sides

Next you know the total number of sides is 30 and you just figured out that your 3 blue tiles have a total of 15 sides so you can subtract 15 from 30 to find how many sides are left

30 - 15 = 15sides

Since you know that these are not blue tiles because in the question it stated that you have 3 blue tiles. These have to be sides for red tiles.

Each red tile have 3 sides so you can divide 15 by 3

15/3 = 5

There are 5 red tiles

You are the number 5