Solution:

It is perfectly feasible. The forty elephants had forty foreheads.

Solution:

After five minutes, the second friend turned around to see if anyone was there or not. At this moment, he was stabbed on back by his friend.

Solution:

The worth of that coin is zero. This is because the B.C. and A.D. dating system was not empowered till the year 525. So the coin is probably fake.

Solution:

He is a barber.

Solution:

b+g = 8

Explanation:
for b in range(1,99):
for g in range(1,99):
sum1=2*b*g+42
sum2=(b+g)*(b+g+1)
if(sum1==sum2):
print(b,g,sum1)

(b,g)=(3,5) => b+g=8

Solution:

It is at the North Pole.

The winds are blowing towards the north till they reach the pole. The moment the pole is crossed, they are blowing towards south.

Solution:

One of the parrot have just decided to fly away. It has not yet taken that action. Thus, there are still six parrots sitting on the branch of the tree.

Solution:

Sweden and Denmark ---> Swedenmark
Russia and Belarus ---> Belarussia

Like we said, there can be many other combinations. If you have found some ones other than these, use the comments section.

Solution:

I am on cloud 9.

Solution:

The easiest method to solve this question will be to form equations.

From the first picture
Weight of Cat + Weight of Rabbit = 10 Kg ---- First Equation

From the second picture
Weight of Dog + Weight of Rabbit = 20 Kg ---- Second Equation

From third picture
Weight of Cat + Weight of Dog = 24 Kg ---- Third Equation

Add the first, second and the third equations.

2 (Weight of Cat) + 2 (Weight of Dog) + 2 (Weight of Rabbit) = 10 Kg + 20 Kg + 24 Kg
2 (Weight of Cat + Weight of Dog + Weight of Rabbit) = 54 Kg
Weight of Cat + Weight of Dog + Weight of Rabbit = 27 Kg