| ( | 16 | + | 20 | ) | × | 5 | + | ( | 16 | + | 25 | ) | × | 2 | + | ( | 18 | + | 16 | ) | ( | X | − | 5 | ) | ( | X | − | 7 | ) | = | 900 |
| 方程左边 = | 16 | × | 5 | + | 20 | × | 5 | + | ( | 16 | + | 25 | ) | × | 2 | + | ( | 18 | + | 16 | ) | ( | X | − | 5 | ) | ( | X | − | 7 | ) |
| = | 80 | + | 100 | + | ( | 16 | + | 25 | ) | × | 2 | + | ( | 18 | + | 16 | ) | ( | X | − | 5 | ) | ( | X | − | 7 | ) |
| = | 180 | + | ( | 16 | + | 25 | ) | × | 2 | + | ( | 18 | + | 16 | ) | ( | X | − | 5 | ) | ( | X | − | 7 | ) |
| = | 180 | + | 16 | × | 2 | + | 25 | × | 2 | + | ( | 18 | + | 16 | ) | ( | X | − | 5 | ) | ( | X | − | 7 | ) |
| = | 180 | + | 32 | + | 50 | + | ( | 18 | + | 16 | ) | ( | X | − | 5 | ) | ( | X | − | 7 | ) |
| = | 262 | + | ( | 18 | + | 16 | ) | ( | X | − | 5 | ) | ( | X | − | 7 | ) |
| = | 262 | + | 18 | ( | X | − | 5 | ) | ( | X | − | 7 | ) | + | 16 | ( | X | − | 5 | ) | ( | X | − | 7 | ) |
| = | 262 | + | 18 | X | ( | X | − | 7 | ) | − | 18 | × | 5 | ( | X | − | 7 | ) | + | 16 | ( | X | − | 5 | ) | ( | X | − | 7 | ) |
| = | 262 | + | 18 | X | ( | X | − | 7 | ) | − | 90 | ( | X | − | 7 | ) | + | 16 | ( | X | − | 5 | ) | ( | X | − | 7 | ) |
| = | 262 | + | 18 | X | X | − | 18 | X | × | 7 | − | 90 | ( | X | − | 7 | ) | + | 16 | ( | X | − | 5 | ) | ( | X | − | 7 | ) |
| = | 262 | + | 18 | X | X | − | 126 | X | − | 90 | ( | X | − | 7 | ) | + | 16 | ( | X | − | 5 | ) | ( | X | − | 7 | ) |
| = | 262 | + | 18 | X | X | − | 126 | X | − | 90 | X | + | 90 | × | 7 | + | 16 | ( | X | − | 5 | ) |
| = | 262 | + | 18 | X | X | − | 126 | X | − | 90 | X | + | 630 | + | 16 | ( | X | − | 5 | ) | ( | X | − | 7 | ) |
| = | 892 | + | 18 | X | X | − | 216 | X | + | 16 | ( | X | − | 5 | ) | ( | X | − | 7 | ) |
| = | 892 | + | 18 | X | X | − | 216 | X | + | 16 | X | ( | X | − | 7 | ) | − | 16 | × | 5 | ( | X | − | 7 | ) |
| = | 892 | + | 18 | X | X | − | 216 | X | + | 16 | X | ( | X | − | 7 | ) | − | 80 | ( | X | − | 7 | ) |
| = | 892 | + | 18 | X | X | − | 216 | X | + | 16 | X | X | − | 16 | X | × | 7 |
| = | 892 | + | 18 | X | X | − | 216 | X | + | 16 | X | X | − | 112 | X | − | 80 |
| = | 892 | + | 18 | X | X | − | 328 | X | + | 16 | X | X | − | 80 | ( | X | − | 7 | ) |
| = | 892 | + | 18 | X | X | − | 328 | X | + | 16 | X | X | − | 80 | X | + | 80 |
| = | 892 | + | 18 | X | X | − | 328 | X | + | 16 | X | X | − | 80 | X | + | 560 |
| = | 1452 | + | 18 | X | X | − | 408 | X | + | 16 | X | X |
| 1452 | + | 18 | X | X | − | 408 | X | + | 16 | X | X | = | 900 |