Solution:

450

Explanation:
II - IV + IX = 200
=> VII = 200

VI + I - V = 100
=> II =100

II - VI + VII = 150
=> III = 150

Therefore,
VII + II + III = 200 + 100 + 150 = 450

Solution:

18 * 12 / 6 + 4

Solution:

1611

Explanation:
The number on the right side is formed as (sum of digits of the 1st number)(number1/number2)
example,
24 $ 6 = 64 (2+4 = 6) (24/6 = 4)
35 $ 5 = 87 (3+5=8) (35/5 = 7)
63 $ 7 = 99 (6+3 =9) (63/7 =9)

Simillarly,
88 $ 8 = (8+8 = 16) (88/8 = 11)

Solution:

The solution is:
547809 + 087549 + 780954 = 1416312

Solution:

    35997
+ 284508
========
    320505
========

Solution:

17

Explanation :
The relationship holds for below formula :
pow(x,3) - pow(x,2) - 1
=> 9*9*9 - 9*9 - 1
=> 729 - 81 - 1
=> 647

Similarly,
17*17*17 - 17*17 - 1
=> 4913 - 289 - 1
=> 4623

Solution:

522

Explanation:
1st Number = Number of alphabtes
2nd Number = Number of vowels
3rd Nummber = Number Of Circles

Lavesh = 6 alphabets + 2 vowels(a,e) + 2 circles(in 'a' and in 'e') = 622
Anmol = 5 alphabets + 2 vowels(a,0) + 2 circles(in 'a' and in 'e') = 522
Shruti = 6 alphabets + 2 vowels(u,i) + 0 circles = 620
Aakriti = 7 alphabets + 4 vowels(a,a,i,i) + 2 circles(in 'A' and in 'a') = 742
Hence,
Sonal = 5 alphabets + 2 vowels(a,o) + 2 circles(in 'a' and in 'o') = 522

Solution:

80

Explanation:
21 B 7 C 9 D 10 A 13
= 21 / 7 + 9 X 10 - 13
= 3 + 90 - 13
= 80

Solution:

HEAVEN

Explanation:
ENEMY = 4 + 3 + 4 + 4 + 3 = 18
LINK = 2 + 1 + 3 + 3 = 9
HELL = 3 + 4 + 2 + 2 = 11
TAXI = 2 + 3 + 2 + 1 = 8
HEAVEN = 3 + 4 + 3 + 2 + 4 + 3 = 19

Using the same trick,
TAXI + HELL = 8 + 11 = 19 = HEAVEN.

Therefore, the required answer is HEAVEN.

Solution:

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

For the full multiplication, see the figure.