I have branches, but no fruit, trunk or leaves. What am I?

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

P is the father of Q and S is the son of R. T is the brother of P and has a daughter U. If R is the sister of P, then what is the relation between U, Q and S?

John’s parents have three sons: Snap, Crackle, and what’s the name of the third son?

There is a box full of marbles,
all but two are blue,
all but two are green,
and all but two are red.

How many marbles are in the box?

What's the next in the series?

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

What breaks yet never falls, and what falls yet never breaks?

What does below Rebus say?

XLR8

What work can one never finish?

Considering the below equation:

V + II - VI = 10
IV - X + VIII = 20
IV - VII + VI = 30

Then, I + II + III = ?