| ( | 100 | + | 1200 | ) | × | 10 | × | 1 2 | + | 1 10 | ( | 100 | + | 1200 | ) | × | 10 | − | 40 | × | 10 | − | 40 | x | = | ( | 100 | + | 1200 | ) | x |
| Left side of the equation = | ( | 100 | + | 1200 | ) | × | 5 | + | 1 | ( | 100 | + | 1200 | ) | − | 400 | − | 40 | x |
| ( | 100 | + | 1200 | ) | × | 5 | + | 1 | ( | 100 | + | 1200 | ) | − | 400 | − | 40 | x | = | ( | 100 | + | 1200 | ) | x |
| Left side of the equation = | 100 | × | 5 | + | 1200 | × | 5 | + | 1 | ( | 100 | + | 1200 | ) | − | 400 | − | 40 | x |
| = | 500 | + | 6000 | + | 1 | ( | 100 | + | 1200 | ) | − | 400 | − | 40 | x |
| = | 6100 | + | 1 | ( | 100 | + | 1200 | ) | − | 40 | x |
| = | 6100 | + | 1 | × | 100 | + | 1 | × | 1200 | − | 40 | x |
| = | 6100 | + | 100 | + | 1200 | − | 40 | x |
| = | 7400 | − | 40 | x |
| 7400 | − | 40 | x | = | ( | 100 | + | 1200 | ) | x |
| Right side of the equation = | 100 | x | + | 1200 | x |
| = | 1300 | x |
| 7400 | − | 40 | x | = | 1300 | x |
| - | 40 | x | − | 1300 | x | = | - | 7400 |
| - | 1340 | x | = | - | 7400 |
| 7400 | = | 1340 | x |
| 1340 | x | = | 7400 |
| x | = | 7400 | ÷ | 1340 |
| = | 7400 | × | 1 1340 |
| = | 370 | × | 1 67 |
| x | = | 370 67 |
| x | = | 5.522388 |