Answer:
A = 2, the number is 3221
Step-by-step explanation:
In order for the number to be divisible by 9, the sum of it's digit has to be divisible by 9.
In our case,
where k is an integer. the easiest way happens when k=1

Higher values of k will likely most work (with k=2 you get A to be a non-integer, which can't work since it's the digit of a number, and with higher values of K you're not getting a number in base 10.
32 is the constant because it doesn’t have a letter
What are you asking for exactly ?
The opposite angles of a parallelogram are congruent, so you have to set the values of each angle equal to each other and solve for x.
(10x-19)° = (7x+23)°
-7x -7x
3x-19 = 23
+19 +19
3x = 43
÷3 ÷3
x = 43
Then, substitute the value of x back into the equations.
(10x-19)°
(10(14)-19)°
(140-19)°
121°
(7x+23)°
(7(14)+23)°
(98+23)°
121°

Actually Welcome to the Concept of the Similarities.
Since here, first figure is a Triangle, hence similarity of a triangle is given by ratio of it sides and make them equate,
hence for,
1.) 16/12 = x/9 ===> 4/3 = x/9 ===> x = 9*4/3 ==> x = 36/3
hence the value of x is 12 , ===> x = 12 .
2.) here,in the case of a Reactangle the relation is such that, length = 2* breadth,
hence we apply the relation,
x = 2*4.5 ===> x = 9 units.