| x | × | 1600 | + | 21 2 | × | 400 | = | 15 2 | × | 2000 |
| Left side of the equation = | x | × | 1600 | + | 4200 |
| 1600 | x | + | 4200 | = | 15 2 | × | 2000 |
| Right side of the equation = | 15000 |
| 1600 | x | + | 4200 | = | 15000 |
| 1600 | x | = | 15000 | − | 4200 |
| 1600 | x | = | 10800 |
| x | = | 10800 | ÷ | 1600 |
| = | 10800 | × | 1 1600 |
| = | 27 | × | 1 4 |
| x | = | 27 4 |
| x | = | 6.75 |