( | 23 | − | x | ) | ( | 400 | − | 20 | x | ) | = | 8400 |
Left side of the equation = | 23 | ( | 400 | − | 20 | x | ) | − | x | ( | 400 | − | 20 | x | ) |
= | 23 | × | 400 | − | 23 | × | 20 | x | − | x | ( | 400 | − | 20 | x | ) |
= | 9200 | − | 460 | x | − | x | ( | 400 | − | 20 | x | ) |
= | 9200 | − | 460 | x | − | x | × | 400 | + | x | × | 20 | x |
= | 9200 | − | 860 | x | + | x | × | 20 | x |
9200 | − | 860 | x | + | x | × | 20 | x | = | 8400 |