Why I cant solve this puzzle? - dart

Question

Im tring to solve this puzzle by using dart lang but I didint solve it and I got large number + error! There is an puzzle image to understand it from here
can you help or give me a tip to solve this puzzle ~!
See full code :
import 'dart:math';
void main() {
var value;
int loob = 0;
do {
var z = new Random().nextInt(20);
var x = new Random().nextInt(20);
var y = new Random().nextInt(20);
var n = new Random().nextInt(20);
if (z - x == 9) {
print('DONE LOOB1 Z = $z and X = $x');
do {
var x = new Random().nextInt(20);
var n = new Random().nextInt(20);
if (x + n == 2) {
print('DONE LOOB2 X = $x and n = $n ');
do {
var n = new Random().nextInt(20);
var y = new Random().nextInt(20);
if (y - n == 14) {
print('DONE LOOB3 y = $y and n = $n ');
do {
var z = new Random().nextInt(20);
var y = new Random().nextInt(20);
if (z - y == 12) {
print('DONE LOOB4 z = $z and y = $y ');
value = 1;
} else {}
} while (value != 1);
} else {}
} while (value != 1);
value = 1;
} else {}
} while (value != 1);
value = 1;
} else {
null;
}
print(++loob);
} while (value != 1);
}
reslate code :
DONE LOOB1 Z = 11 and X = 2
DONE LOOB2 X = 2 and n = 0
DONE LOOB3 y = 14 and n = 0
DONE LOOB4 z = 17 and y = 5
Finshed

Answer 1

this is your algorithm issue, you are adding 0.1 to your variable every step, and it means all numbers are equal in the end you must create two mathematical equations and two unknown values and then solve them. this is the main approach to solve such problems.
Assume this picture like these Equations:
x - y = 9
x + n = 2
y - n = 14
z - y = 12
now you have 4 equations and 4 unknown.
you can solve this equation by this (Matrix manipulation) or this (substitution one unknown with another) on method.