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

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

How many times do a clock's hands overlap in a day ?

I look at you, you look at me, I raise my right, you raise your left. What am I?

Forwards I am heavy, backward I am not. What am I?

Can you discover the missing number in this series?

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

What is the largest amount of money that you can possess in change and still if someone asks you for a dollar, you won't be able to give?

What mathematical symbol can be put between 5 and 9, to get a number bigger than 5 and smaller than 9?

If I remove one from eleven it becomes Ten and if I remove one from nine also becomes Ten. How?

Use the digits from 1 up to 9 and make 100.

Follow the rules.
=> Each digit should be used only once.
=> You can only use addition.
=> For making a number, two single digits can be combined (for example, 4 and 2 can be combined to form 42 or 24)
=> A fraction can also be made by combining the two single digits (for example, 4 and 2 can be combined to form 4/2 or 2/4)

Question: how can we do this?

What is the centre of gravity?