what does the below math rebus puzzle mean?

I am first found in caves, now prolific online; I am a depiction, a drawing, a symbol, or sign. I will convey whichever mood you could wish; or for that matter, a fist, flask, or fish. What am I?

A man has to get a fox, a chicken, and a sack of corn across a river.

He has a rowboat, and it can only carry him and one other thing.
If the fox and the chicken are left together, the fox will eat the chicken.
If the chicken and the corn are left together, the chicken will eat the corn.

How does the man do it?

What is the four-digit number in which the first digit is one-third the second, the third is the sum of the first two, and the last is three times the second?

Can you discover the missing number in this series?

37, 10, 82
29, 11, 47
96, 15, 87
42, ?, 15

What goes up but never comes down?

Find the Next Number in the Sequence

2 9 3 1 8 4 3 6 5 7 ?

There was a strange boy who was born before his father. How can this be possible?

Can you count the number of triangles inside a triangle?

How many triangles are there in the picture below?