99 100 | X | = | 99 1000 | ( | 99 | + | X | ) |
| Right side of the equation = | 99 1000 | × | 99 | + | 99 1000 | X |
| = | 9801 1000 | + | 99 1000 | X |
99 100 | X | = | 9801 1000 | + | 99 1000 | X |
99 100 | X | − | 99 1000 | X | = | 9801 1000 |
891 1000 | X | = | 9801 1000 |
| X | = | 9801 1000 | ÷ | 891 1000 |
| = | 9801 1000 | × | 1000 891 |
| = | 11 | × | 1 |
| X | = | 11 |