| 84900 | = | x | + | x | × | 21 20 | + | x | × | 21 20 | × | 21 20 |
| Right side of the equation = | x | + | x | × | 21 20 | + | x | × | 441 400 |
| = | 1261 400 | x |
| 84900 | = | 1261 400 | x |
| - | 1261 400 | x | = | - | 84900 |
| 84900 | = | 1261 400 | x |
1261 400 | x | = | 84900 |
| x | = | 84900 | ÷ | 1261 400 |
| = | 84900 | × | 400 1261 |
| x | = | 33960000 1261 |
| x | = | 26931.007137 |