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 = ?

What jumps when it walks and sits when it stands?

Which is the smallest number that you can write using all the vowels exactly once?

In a school, there are four subjects. Seventy percent of students study English, seventy five percent of students study Science, eighty five percent of students study Mathematics and eighty percent of students study Spanish.

Can you calculate the percentage of students that study all four subjects?

Move three sticks of the spiral below to form a square.

How do you go from 98 to 720 using just one letter?

A number can be multiplied by multiple of nine
i.e 9 18 27 36 45 ...

and the resulting number consist of only one digit.

Can you identify the number ?

What Adam and Eve do not have but the rest of the people have?

Analyze and find the missing item in the sequence:
16, 06, 68, 88, __, 98

I am a type of room you cannot enter or leave. Raised from the ground below, I could be poisonous or a delicious treat. What am I?