4/5 (four fifth) of 500 pages is

times 500

times 500 is

,
which is

So Dayo read 400 pages of 500.
Dayo has not yet read 500-400=100 pages.
Answer: 100
You did not include the context in which your question was asked so I cannot help you with this. If you were to add some context, then I'll try my best to help you! :)
Since a plane is 180 degrees total, x=135
180-45=135
Answer:
1. keep counting
2. He can do 5 times 3 to get to the 15th shape and then say 2 more to get the 17th shape.
(The 17th shape would be triangle)