Solution:

Man1 is carrying 5 bags and the Man2 is carrying 7 bags.

Let's assume that the Man1 was carrying M1 bags and the Man2 was carrying M2 bags.
M2 + 1 = 2 * (X-1)
M2 + 1 = 2M1 - 2
M2 = 2M1 - 3

Also,
M2 - 1 = M1 + 1
M2 = M1 + 2

=>
2M1 - 3 = M1 + 2
M1 = 5

=>
M2 = 7

Solution:

8

Solution:

3

Solution:

10968

Water image is 89601

Solution:

117(1+3+5,3+4)

Solution:

12

Solution:

48 minutes.

Donald duck's speed = X km/seconds
pool current speed = Y km/seconds

2/(X+Y) = 40
2/(X-Y) = 60

Solving the simultaneous equations gives X = 1/24

Therefore, to cover 2km will take 2/X = 48 seconds

Solution:

Marshall lives in House no.36
Robin lives in House no.4
Barney lives in House no.9
Lily lives in House no.35
Lyndsy lives in House no.24

Solution:

1st fish tank-> 5

2nd fish tank-> 7

Solution:

3 hours

Explanation :
(1/4 + 1/6 - 1/12) ^ (-1)
= (1/3)^(-1) = 3