| ( | 1 | + | 2 | + | 3 | + | 4 | ) | ÷ | 5 | + | ( | 100 | ( | ( | X | − | ( | 1 | + | 2 | + | 3 | + | 4 | + | 5 | + | 6 | + | 7 | + | 8 | + | 9 | + | 10 | + | 1 | + | 12 | ) | ÷ | 20 | + | X | ÷ | 20 | ) | ) | ÷ | 5 | ) | = | 0 |
| Left side of the equation = | 1 | × | 1 5 | + | 2 | × | 1 5 | + | 3 | × | 1 5 | + | 4 | × | 1 5 | + | ( | 100 | ( | ( | X | − | ( | 1 | + | 2 | + | 3 | + | 4 | + | 5 | + | 6 | + | 7 | + | 8 | + | 9 | + | 10 | + | 1 | + | 12 | ) | ÷ | 20 | + | X | ÷ | 20 | ) | ) | ÷ | 5 | ) |
| = | 1 5 | + | 2 5 | + | 3 5 | + | 4 5 | + | ( | 100 | ( | ( | X | − | ( | 1 | + | 2 | + | 3 | + | 4 | + | 5 | + | 6 | + | 7 | + | 8 | + | 9 | + | 10 | + | 1 | + | 12 | ) | ÷ | 20 | + | X | ÷ | 20 | ) | ) | ÷ | 5 | ) |
| = | 2 | + | ( | 100 | ( | ( | X | − | ( | 1 | + | 2 | + | 3 | + | 4 | + | 5 | + | 6 | + | 7 | + | 8 | + | 9 | + | 10 | + | 1 | + | 12 | ) | ÷ | 20 | + | X | ÷ | 20 | ) | ) | ÷ | 5 | ) |
| = | 2 | + | 100 | ( | ( | X | − | ( | 1 | + | 2 | + | 3 | + | 4 | + | 5 | + | 6 | + | 7 | + | 8 | + | 9 | + | 10 | + | 1 | + | 12 | ) | ÷ | 20 | + | X | ÷ | 20 | ) | ) | ÷ | 5 |
| = | 2 | + | 20 | ( | ( | X | − | ( | 1 | + | 2 | + | 3 | + | 4 | + | 5 | + | 6 | + | 7 | + | 8 | + | 9 | + | 10 | + | 1 | + | 12 | ) | ÷ | 20 | + | X | ÷ | 20 | ) | ) |
| = | 2 | + | 20 | ( | X | − | ( | 1 | + | 2 | + | 3 | + | 4 | + | 5 | + | 6 | + | 7 | + | 8 | + | 9 | + | 10 | + | 1 | + | 12 | ) | ÷ | 20 | + | X | ÷ | 20 | ) |
| = | 2 | + | 20 | X | − | 20 | ( | 1 | + | 2 | + | 3 | + | 4 | + | 5 | + | 6 | + | 7 | + | 8 | + | 9 | + | 10 | + | 1 | + | 12 | ) | ÷ | 20 | + | 20 | X | ÷ | 20 |
| = | 2 | + | 20 | X | − | 1 | ( | 1 | + | 2 | + | 3 | + | 4 | + | 5 | + | 6 | + | 7 | + | 8 | + | 9 | + | 10 | + | 1 | + | 12 | ) | + | 1 | X |
| = | 2 | + | 21 | X | − | 1 | ( | 1 | + | 2 | + | 3 | + | 4 | + | 5 | + | 6 | + | 7 | + | 8 | + | 9 | + | 10 | + | 1 | + | 12 | ) |
| = | 2 | + | 21 | X | − | 1 | × | 1 | − | 1 | × | 2 | − | 1 | × | 3 | − | 1 | × | 4 | − | 1 |
| = | 2 | + | 21 | X | − | 1 | − | 2 | − | 3 | − | 4 | − | 5 | − | 6 | − | 7 | − | 8 | − | 9 |
| = | - | 178 | + | 21 | X |
| - | 178 | + | 21 | X | = | 0 |
| 21 | X | = | 0 | + | 178 |
| 21 | X | = | 178 |
| X | = | 178 | ÷ | 21 |
| = | 178 | × | 1 21 |
| X | = | 178 21 |
| X | = | 8.47619 |