| 20 | x | × | 80 100 | = | 20 | ( | x | − | 7 | ) | × | 90 |
| Left side of the equation = | 16 | x |
| 16 | x | = | 20 | ( | x | − | 7 | ) | × | 90 |
| Right side of the equation = | 1800 | ( | x | − | 7 | ) |
| 16 | x | = | 1800 | ( | x | − | 7 | ) |
| Right side of the equation = | 1800 | x | − | 1800 | × | 7 |
| = | 1800 | x | − | 12600 |
| 16 | x | = | 1800 | x | − | 12600 |
| 16 | x | − | 1800 | x | = | - | 12600 |
| - | 1784 | x | = | - | 12600 |
| 12600 | = | 1784 | x |
| 1784 | x | = | 12600 |
| x | = | 12600 | ÷ | 1784 |
| = | 12600 | × | 1 1784 |
| = | 1575 | × | 1 223 |
| x | = | 1575 223 |
| x | = | 7.06278 |