| 15 | + | 15 | ( | 1 | + | X | ) | + | 15 | ( | 1 | + | X | ) | ( | 1 | + | X | ) | = | 60 |
| Left side of the equation = | 15 | + | 15 | × | 1 | + | 15 | X | + | 15 | ( | 1 | + | X | ) | ( | 1 | + | X | ) |
| = | 15 | + | 15 | + | 15 | X | + | 15 | ( | 1 | + | X | ) | ( | 1 | + | X | ) |
| = | 30 | + | 15 | X | + | 15 | ( | 1 | + | X | ) | ( | 1 | + | X | ) |
| = | 30 | + | 15 | X | + | 15 | × | 1 | ( | 1 | + | X | ) | + | 15 | X | ( | 1 | + | X | ) |
| = | 30 | + | 15 | X | + | 15 | ( | 1 | + | X | ) | + | 15 | X | ( | 1 | + | X | ) |
| = | 30 | + | 15 | X | + | 15 | × | 1 | + | 15 | X | + | 15 | X | ( | 1 | + | X | ) |
| = | 30 | + | 15 | X | + | 15 | + | 15 | X | + | 15 | X | ( | 1 | + | X | ) |
| = | 45 | + | 30 | X | + | 15 | X | ( | 1 | + | X | ) |
| = | 45 | + | 30 | X | + | 15 | X | × | 1 | + | 15 | X | X |
| = | 45 | + | 30 | X | + | 15 | X | + | 15 | X | X |
| = | 45 | + | 45 | X | + | 15 | X | X |
| 45 | + | 45 | X | + | 15 | X | X | = | 60 |