How to solve 4/9=28/x in two methods

Proportion:

a/b = c/d

where: cross products are equal.
ad = bc
                    a/b = c/d
a = 4            4/9 = 28/x
b = 9            cross products
c = 28          ad = bc
d = x            4x = 9*28
                    4x = 252
                    4x/4 = 252/4
                      x = 63
4/9 = 28/x
4/9 = 28/63
4/9 is the simplified factor of 28/63. 
28 ÷ 7 = 4
63 ÷ 7 = 9

Another solution for this is.
4/9 = 28/x

x is a denominator, we need to eliminate it. To do so, we must make x the numerator. so we multiply both side with x.

4/9 * x/1 = 28/x * x/1
4x/9 = 28
4x/9 * 9/1 = 28 * 9/1   *eliminate the denominator 9 by multiplying both                                          sides with numerator 9.
4x = 252
4x/4 = 252/4
x = 63

The solution to the system of equations (-2,2)