What does this rebus mean?

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Can you count the number of triangles inside a triangle?

I am taken from a mine and shut up in a wooden case, from which I am never released, and yet I am used by almost every person. What am I?

A man stands on one side of a river, his dog on the other. The man calls his dog, who immediately crosses the river without getting wet and without using a bridge or a boat. How did the dog do it?

I live in a bowl. I can swim. I have a tail. I also have fins and big eyes. What am I?

Many have heard it, but nobody has ever seen it, and it will not speak back until spoken to. What is it?

If 5 cats catch 5 mice in 5 minutes, how long will it take one cat to catch a mouse?

I am the black child of a white father, a wingless bird, flying even to the clouds of heaven. I give birth to tears of mourning in pupils that meet me, even though there is no cause for grief, and at once on my birth, I am dissolved into air. What am I?

Consider all the numbers between 1 and 1 million. Among all these numbers, there is something very special about the number 8 and the number 2202. What is it?

What is the below Rebus indicate?