Can you solve this tricky maths equation problem by replacing it? mark with the correct symbol?

19834 -----: 187
15921 -----: 153
17561 -----: 139
13734 -----: ???

The host of a game show, offers the guest a choice of three doors. Behind one is a expensive car, but behind the other two are goats.
After you have chosen one door, he reveals one of the other two doors behind which is a goat (he wouldn't reveal a car).

Now he gives you the chance to switch to the other unrevealed door or stay at your initial choice. You will then get what is behind that door.

You cannot hear the goats from behind the doors, or in any way know which door has the prize.

Should you stay, or switch, or doesn't it matter?

If 2 workers can complete painting 2 walls in exactly 2 hours.

How many workers would be needed to paint 18 walls in 6 hours?

What is 3/7 chicken, 2/3 cat and 2/4 goat?

Decode below three cipher riddles:

26 L of the A
7 D of the W
1000 Y in a M

How can you write nineteen in a manner that if we take out one, it becomes twenty?

If you toss a coin 10 times and it lands heads up every time, what are the chances it will land heads up if you toss it again?

I start and end with 500 and carry a 5 in my heart. But I require the first letter and the first number to be complete. I am the name of a King.

Who am I ?

Look at the picture and find out which square is not linked with any of the other squares.

A word I know has six letters it contains, remove one letter and 12 remain. What is it?