| 70 | = | ( | x | + | ( | 120 | − | x | ) | ) | ÷ | 120 | × | 100 |
| Right side of the equation = | ( | x | + | ( | 120 | − | x | ) | ) | × | 5 6 |
| 70 | = | ( | x | + | ( | 120 | − | x | ) | ) | × | 5 6 |
| Right side of the equation = | x | × | 5 6 | + | ( | 120 | − | x | ) | × | 5 6 |
| = | 5 6 | x | + | 120 | × | 5 6 | − | x | × | 5 6 |
| = | 5 6 | x | + | 100 | − | x | × | 5 6 |
| = | 0 | x | + | 100 |
| 70 | = | 100 |
| = | 100 | − | 70 |