| ( | x | − | 90 | ) | × | 3 4 | ÷ | 100 | = | ( | x | − | 40 | ) | × | 3 4 | ÷ | 125 |
| Left side of the equation = | ( | x | − | 90 | ) | × | 3 400 |
| ( | x | − | 90 | ) | × | 3 400 | = | ( | x | − | 40 | ) | × | 3 4 | ÷ | 125 |
| Left side of the equation = | x | × | 3 400 | − | 90 | × | 3 400 |
| = | x | × | 3 400 | − | 27 40 |
3 400 | x | − | 27 40 | = | ( | x | − | 40 | ) | × | 3 4 | ÷ | 125 |
| Right side of the equation = | ( | x | − | 40 | ) | × | 3 500 |
3 400 | x | − | 27 40 | = | ( | x | − | 40 | ) | × | 3 500 |
| Right side of the equation = | x | × | 3 500 | − | 40 | × | 3 500 |
| = | x | × | 3 500 | − | 6 25 |
3 400 | x | − | 27 40 | = | 3 500 | x | − | 6 25 |
3 400 | x | − | 3 500 | x | = | - | 6 25 | + | 27 40 |
3 2000 | x | = | - | 6 25 | + | 27 40 |
3 2000 | x | = | 87 200 |
| x | = | 87 200 | ÷ | 3 2000 |
| = | 87 200 | × | 2000 3 |
| = | 29 | × | 10 |
| x | = | 290 |