| ( | 200 | − | y | − | 156 | ) | ( | 20 | + | 5 | y | ) | = | 1600 |
| Left side of the equation = | 200 | ( | 20 | + | 5 | y | ) | − | y | ( | 20 | + | 5 | y | ) | − | 156 | ( | 20 | + | 5 | y | ) |
| = | 200 | × | 20 | + | 200 | × | 5 | y | − | y | ( | 20 | + | 5 | y | ) | − | 156 | ( | 20 | + | 5 | y | ) |
| = | 4000 | + | 1000 | y | − | y | ( | 20 | + | 5 | y | ) | − | 156 | ( | 20 | + | 5 | y | ) |
| = | 4000 | + | 1000 | y | − | y | × | 20 | − | y | × | 5 | y | − | 156 | ( | 20 | + | 5 | y | ) |
| = | 4000 | + | 980 | y | − | y | × | 5 | y | − | 156 | ( | 20 | + | 5 | y | ) |
| = | 4000 | + | 980 | y | − | y | × | 5 | y | − | 156 | × | 20 | − | 156 | × | 5 | y |
| = | 4000 | + | 980 | y | − | y | × | 5 | y | − | 3120 | − | 780 | y |
| = | 880 | + | 200 | y | − | y | × | 5 | y |
| 880 | + | 200 | y | − | y | × | 5 | y | = | 1600 |