| ( | 210 | − | 190 | − | x | ) | ( | 8 | + | 2 | x | ) | = | 280 |
| Left side of the equation = | 210 | ( | 8 | + | 2 | x | ) | − | 190 | ( | 8 | + | 2 | x | ) | − | x | ( | 8 | + | 2 | x | ) |
| = | 210 | × | 8 | + | 210 | × | 2 | x | − | 190 | ( | 8 | + | 2 | x | ) | − | x | ( | 8 | + | 2 | x | ) |
| = | 1680 | + | 420 | x | − | 190 | ( | 8 | + | 2 | x | ) | − | x | ( | 8 | + | 2 | x | ) |
| = | 1680 | + | 420 | x | − | 190 | × | 8 | − | 190 | × | 2 | x | − | x | ( | 8 | + | 2 | x | ) |
| = | 1680 | + | 420 | x | − | 1520 | − | 380 | x | − | x | ( | 8 | + | 2 | x | ) |
| = | 160 | + | 40 | x | − | x | ( | 8 | + | 2 | x | ) |
| = | 160 | + | 40 | x | − | x | × | 8 | − | x | × | 2 | x |
| = | 160 | + | 32 | x | − | x | × | 2 | x |
| 160 | + | 32 | x | − | x | × | 2 | x | = | 280 |