Solution:

7 years.

Explanation:
Kylian * Thorgan * Eden = 175
and only value that fits in above equation is:
Kylian = Thorgan = 5years
Eden = 7 years

Solution:

20 more bullets

Explanation:
Initially, Willian has 'W' bullets and Pedro has 'P' bullets.

Based on statements, we have 2 equations
3P = W
2(P+10) = W-10

=> 2P + 20 = 3P - 10
=> 30 = P

P = 30 and W = 90.

Willian gave 10 bullets, therefore, need to give 20 more bullets so that they can 60 bullets each.

Solution:

28745

Explanation

New Number = (Last Number +1 ) * 9
and Then New Number = (Last Number - 1 ) * 8 and so on.

i.e
1
(1+1) * 9 = 18
(18-1) * 8 = 136
(136+1) * 7 = 959
(959-1) * 6 = 5748
(5748+1) * 5 = 28745
(28745-1) * 4 = 114976
(114976+1) * 3 = 344931

Solution:

0(zero) off course.

Solution:

120 km

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
========