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

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

You have a three-gallon and a five-gallon measuring device. You wish to measure out four gallons.

What is red and smells like blue paint?

You and your two friends are working in a multinational company. How can you three find out the average salary of you all without disclosing your own salary to the other two?

What has 13 hearts but no other organs?

Can you find a pattern and the missing number in the series given below?

100, 155, 258,? , 584, 819.

I have two sand hourglasses:
1. A 7 minute one and
2. An 11-minute one.

Using just these 2 sand hourglasses, how can I measure time as 15 minutes?

If an electric train is travelling south, then which way is the smoke going?

who is silent in the parliament?

There are four 3-link chains. All you have to do is join them into a big 12-link chain. For joining two closed links, one of the links must be cut and placed onto the other link for closing.

How many minimum links will you have to cut to make the big chain?