Solution:

Eye

Explanation :
It is written with two letters. ( 'E' and 'y')
It is said with the one. ( I )
It usually is seen with the two. ( two eyes)

Solution:

5

Explanation
First three equation in the image can be written as :
a) 3 BED = 30
b) 2 BED + BUS = 40
c) BED + 2 BUS+ 2 TROPHY = 60

From equation a)
BED = 10

From equation b)
BUS = 40 -20 =20

From equation c)
10 + 40 + 2 TROPHY = 60

TROPHY = 5

Solution:

It can be done as shown below.

Solution:

It can be solved as shown.

Solution:

It can be done as shown below.

Solution:

See the picture for the answer. Don't worry if you have a different answer; this question can be solved with different numbers. However, do post your answer in the comments.

Solution:

Rashid's son-1: 1 11 21 31 41 51 61 71 81
Rashid's son-2: 2 12 22 32 42 52 62 72 73
Rashid's son-3: 3 13 23 33 43 53 63 64 74
Rashid's son-4: 4 14 24 34 44 54 55 65 75
Rashid's son-5: 5 15 25 35 45 46 56 66 76
Rashid's son-6: 6 16 26 36 37 47 57 67 77
Rashid's son-7: 7 17 27 28 38 48 58 58 78
Rashid's son-8: 8 18 19 29 39 49 59 69 79
Rashid's son-9: 9 10 20 30 40 50 60 70 80

Solution:

Nightmare.

Explanation:
(K)night + mare (A mare is the female of a horse)

Solution:

It can be done in 8 moves as shown in the animated image below.

Solution:

The brain teaser can be solved as shown in the image below.