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

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

If 1+9+8=1, what is 2+8+9?

Andrew’s doctor gives him three pills and tells him to take one every half hour. How much time will have passed by the time Andrew’s taken all three pills?

You have four chains. Each chain has three links in it. Although it is difficult to cut the links, you wish to make a single loop with all 12 links. What is the fewest number of cuts you must make to accomplish this task?

The day after tomorrow will be three days before Tuesday. Can you find out what is today?

Find three numbers such that When we multiply three numbers, we will get the prime numbers. The difference between the second and the first number is equal to the third and second.

Who can jump higher than a Mountain?

Can you arrange four 9's and use at most 2 math symbols, to make the total 100?

Decode below three cipher riddles:

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

I can write cow in 13 letters.

Can You?