| 4 | × | 20 | ( | y | ) | ( | 3 | ) | = | 320 | ( | 15 | − | y | ) | ( | 3 | ) |
| Left side of the equation = | 80 | ( | y | ) | ( | 3 | ) |
| 80 | ( | y | ) | ( | 3 | ) | = | 320 | ( | 15 | − | y | ) | ( | 3 | ) |
| Left side of the equation = | 80 | y | ( | 3 | ) |
| = | 80 | y | × | 3 |
| = | 240 | y |
| 240 | y | = | 320 | ( | 15 | − | y | ) | ( | 3 | ) |
| Right side of the equation = | 320 | × | 15 | ( | 3 | ) | − | 320 | y | ( | 3 | ) |
| = | 4800 | ( | 3 | ) | − | 320 | y | ( | 3 | ) |
| = | 4800 | × | 3 | − | 320 | y | ( | 3 | ) |
| = | 14400 | − | 320 | y | ( | 3 | ) |
| = | 14400 | − | 320 | y | × | 3 |
| = | 14400 | − | 960 | y |
| 240 | y | = | 14400 | − | 960 | y |
| 240 | y | + | 960 | y | = | 14400 |
| 1200 | y | = | 14400 |
| y | = | 14400 | ÷ | 1200 |
| = | 14400 | × | 1 1200 |
| = | 12 | × | 1 |
| y | = | 12 |