The more of this there is, the less you see. What is it?

Which number should replace the question mark?

Two old friends, Jack and Bill, meet after a long time.

Three kids
Jack: Hey, how are you, man?
Bill: Not bad, got married and I have three kids now.
Jack: That's awesome. How old are they?
Bill: The product of their ages is 72 and the sum of their ages is the same as your birth date.
Jack: Cool..But I still don't know.
Bill: My eldest kid just started taking piano lessons.
Jack: Oh, now I get it.

How old are Bill's kids?

There is a square of a particular number which when doubled, becomes 7 more than its quarter.

Can you find the number?

I go up and I go down.
I go up towards the beautiful sky and down toward the green ground.
I am present tense.
I am past tense too
Children love me.

Who Am I?

A finger goes in me. You fiddle with me when you're bored. The best man always has me first. What am I?

What's the next in the series?

H, Be, F, S, Mn, Kr, In, Gd, Tl, ?

I never stop running even when I standstill. If I am formed by joining two identical bodies together, can you guess who I am?

I always drive my customer away.

Who am I?

Solve The below Equation:

ALFA + BETA + GAMA = DELTA