What does this mathematical rebus means ?

I have cities, but no houses. I have mountains, but no trees. I have water, but no fish. What am I?

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

You have 10 balls with you. A friend of yours out of nowhere asks you to place those ten balls in five lines such that each of the lines has exactly 4 balls on them. He needs to check your intelligence. Prove him by doing the task.

Find The Odd One Out

1. FLOW
2. SNIP
3. TRAP
4. DRAW
5. BACK

How many pluses should we put between the digits of 987654321 to get a total of 99, and where?

A man started to town with a fox, a goose, and a sack of corn. He came to a stream which he had to cross in a tiny boat. He could only take one across at a time. He could not leave the fox alone with the goose or the goose alone with the corn. How did he get them all safely over the stream?

If 21x = 79x, what is the value of x?

Prove that the below maths equation is true.

8 + 8 = 91

I possess a head

I flaunt a tail

But I don't have mouth or legs

Can you find out who I am?