Solution:

9

Explanation:
5 cartons for large boxes = 5 * 6 = 30 boxes
4 cartons for small boxes = 4 * 9 = 36 boxes

He will need 9 cartons to place 66 boxes.

Solution:

The man is 84 years old.
The son is 49 years old.
The grandson is 7 years old.

Solution:

3 3/4 hours

Explanation:
Suppose that the amount of petrol in each of the cars in the beginning was M.
Now, suppose that they drove for X hours.

In that case, the amount of petrol used by one car in X hours will be = M*X /4
The amount of petrol used by the other car will be = M*X/5

Therefore, the petrol left in one car = M - M*X / 4
Petrol left in the other car = M - M*X / 5

Now, according to the question,
M - M*X / 5 = 4 (M - M*X / 4)
=> X = 15 / 4 = 3 3/4 hours.

Therefore Murphy and Cooper drove for 3 3/4 hours.

Solution:

18

Explanation:
More minutes implies more tea.
More women implies more tea.

The time become twice (3 minutes / 1.5 minutes).
women become six times (9 / 1.5).

Number of tea = 2 * 6 * Original(1.5)
= 18

Solution:

Q>P

Explanation:
P = 60 * 60 * 24 seconds = 86, 400 seconds.
Q = (8 * 365 *24) + (2 * 366 *24) hours = 87, 648 hours

Therefore, Q is greater than P. If the leap years were not counted, results would have been different.

Solution:

T = 1
W = 3
O = 8
H = 9
R = 0
E = 4

For the full multiplication, see the figure.

Solution:

1 * 1 = 1
11 * 11 = 121
111 * 111 = 12321
1111 * 1111 = 1234321


Following the pattern, you can come straight at:
111111111 * 111111111 = 11=2345678987654321

Solution:

The integer with the special property is -1.

To test the property, let us subtract any digit from it, let's say 5.

-1 - 5 = -6

The succeeding digit of 5 is 6.

When (-6) is divided by 6, it is completely divided.

For all other numbers as well, this stands true.

Solution:

84

Explanation:
Let us assume that Adam lived for p years.

p/6 + p/12 + p/7 + 5 + p/2 + 4 = x
=> p = 84.

Therefore, Adam lived for 84 years.

Solution:

25

Distance between Tribe Q and Tribe S = 40km
=> Distance between Tribe Q and Tribe R + Distance between Tribe R and Tribe S = 40km
=> Distance between Tribe Q and Tribe R + (Distance between Tribe Q and Tribe R - 10) = 40 km
=> 2 * Distance between Tribe Q and Tribe R = 50km
=> Distance between Tribe Q and Tribe R = 25km