The French Revolution of 1830, also known as the July Revolution, Second French Revolution or Trois Glorieuses in French, saw the overthrow of King Charles X, the French Bourbon monarch, and the ascent of his cousin Louis-Philippe, Duke of Orléans.

Let us use a  trick to solve it quickly

99x + 101y = 499 ............ i

101x + 99y = 501............ ii

subtract i  from  ii

2x - 2y = 2
x - y =1
x = 1 + y   ........   iii

add i and  ii

200x + 200y = 1000
x + y = 5 .................................. iv

Now from iii and  iv  ,  we get  1 + y + y = 5       or          2y = 4       or        y = 2     ......  v

again from iii and  v   , we get  x = 1 + 2 = 3

Hence x = 3  ,  y = 2

5x + 2y = -3 ........ (i)
x + 5y = 4
x = 4 - 5y ........... (ii)
Put (ii) in (i), we get
5(4 - 5y) + 2y = -3
20 - 15y + 2y =-3
- 13y = - 3 - 20
-13y = -23
y = 23/13
Put value of  y in (ii), we get
x = 4 - 5(23/13)
x = (52 - 5)/13 = 47/3
 

5m - 3n = 19 ......... (i)
m - 6n = -7 ........... (ii)
Multiple (i) by 2 , we get
10m - 6n = 38........... (iii)
Subtract (iii) and (ii), we get
(10m - 6n)- (m - 6n) = 38 - (-7)
10m - 6n - m + 6n = 38 + 7
9m = 45
m = 5
Put m = 5 in (ii) we get
5 - 6n = -7
-6n = -7 - 5
-6n = -12
n = 2

Any number can be written as the product of a number between 1 and 10 and a number which is power of ten. The exponential part of a particular measurement is called order of magnitude of a quantity.
Example: Diameter of Jupiter = 142700000 m = 1.427 x 10⁸ m
  Order of magnitude = exponential part = 10⁸ m   

3x + 2y = 29  .......... (i)
5x - y = 18  .......... (ii) 
multiply equation (ii) by 2 and add in (i) ,  we get
3x + 2y = 29
+10x - 2y = 36
____________
13x=65
x = 65/13=  5
now put in (ii), we get
5(5) - y = 18
25 - y = 18
25 - 18 = y
7 = y
and x = 5

Freezing point depressionΔTf = i × Kf × mi = ΔTf Kf × m    = 7.10 × 10−31.86 × 0.001    =3.82 ≈ 4The total number of value of i = 4The given complex Kx[Fe(CN)6]  has already complex ion [Fe(CN)6] as 1.So the remaining are K ions = 4−1 = 3Thus  the value of x =3 and the complex is K3[Fe(CN)6]