Can you replace the question mark with the correct letter?

6 + 6 + 6 = N
7 + 7 + 7 = E
8 + 8 + 8 = R
0 + 0 + 0 = ?

The centre of the third figure is empty. What digit should fit inside?

I can write cow in 13 letters.

Can You?

John was driving a bus and got stuck when passing through an underpass. Then came Jacob with a needle and got the bus out of the underpass.

What did the boy do?

What goes through cities and fields, but never moves?

What has a ring but no finger?

Move four matchsticks to the below square to form three squares?

Find a 9-digit number, which you will gradually round off starting with units, then tenth, hundred etc., until you get to the last numeral, which you do not round off. The rounding alternates (up, down, up ...). After rounding off 8 times, the final number is 500000000. The original number is commensurable by 6 and 7, all the numbers from 1 to 9 are used, and after rounding four times the sum of the not rounded numerals equals 24.

I travel all around the world but always stay in the corner. What am I?

Can you count the number of triangles in the given picture?