Solution:

Align the toothpicks to form TEN. Use one toothpick for each of the lines.

Solution:

Four

As the window was closed it is obvious that the six candles that were not extinguished were lit till they melted away entirely. Thus only four candles that were extinguished remain at the end.

Solution:

What

Solution:

See o double you

Solution:

Birbal drew another line that was larger than the pre-drawn line. Now the pre drawn line was smaller.

Solution:

Both of them were sitting in the opposite directions of the table with their backs facing each other.

Solution:

I + IX = X

The equation read from the other side becomes X = XI + I which is false.

Solution:

Either your read from start or from ends, it will be same

Solution:

Everyone will done one day or other.

Abraham Lincoln era is too old and we expect most of them(if not all) to be dead by now.

Solution:

I am a secret.