| x | = | ( | 8000 | + | 7200 | + | x | ) | ÷ | 3 | + | 400 |
| Right side of the equation = | 8000 | × | 1 3 | + | 7200 | × | 1 3 | + | x | × | 1 3 | + | 400 |
| = | 8000 3 | + | 2400 | + | x | × | 1 3 | + | 400 |
| = | 16400 3 | + | 1 3 | x |
| x | = | 16400 3 | + | 1 3 | x |
| x | − | 1 3 | x | = | 16400 3 |
2 3 | x | = | 16400 3 |
| x | = | 16400 3 | ÷ | 2 3 |
| = | 16400 3 | × | 3 2 |
| = | 8200 | × | 1 |
| x | = | 8200 |