| ( | 360 | − | 200 | ) | ÷ | ( | 500 | − | 360 | ) | = | ( | A | − | 9 | ) | ÷ | ( | 209 10 | − | A | ) |
| Multiply both sides of the equation by: | ( | 500 | − | 360 | ) | , | ( | 209 10 | − | A | ) |
| ( | 360 | − | 200 | ) | ( | 209 10 | − | A | ) | = | ( | A | − | 9 | ) | ( | 500 | − | 360 | ) |
| 360 | ( | 209 10 | − | A | ) | − | 200 | ( | 209 10 | − | A | ) | = | ( | A | − | 9 | ) | ( | 500 | − | 360 | ) |
| 360 | ( | 209 10 | − | A | ) | − | 200 | ( | 209 10 | − | A | ) | = | A | ( | 500 | − | 360 | ) | − | 9 | ( | 500 | − | 360 | ) |
| 360 | × | 209 10 | − | 360 | A | − | 200 | ( | 209 10 | − | A | ) | = | A | ( | 500 | − | 360 | ) | − | 9 | ( | 500 | − | 360 | ) |
| 360 | × | 209 10 | − | 360 | A | − | 200 | ( | 209 10 | − | A | ) | = | A | × | 500 | − | A | × | 360 | − | 9 | ( | 500 | − | 360 | ) |
| 7524 | − | 360 | A | − | 200 | ( | 209 10 | − | A | ) | = | A | × | 500 | − | A | × | 360 | − | 9 | ( | 500 | − | 360 | ) |
| 7524 | − | 360 | A | − | 200 | ( | 209 10 | − | A | ) | = | 140 | A | − | 9 | ( | 500 | − | 360 | ) |
| 7524 | − | 360 | A | − | 200 | × | 209 10 | + | 200 | A | = | 140 | A | − | 9 | ( | 500 | − | 360 | ) |
| 7524 | − | 360 | A | − | 200 | × | 209 10 | + | 200 | A | = | 140 | A | − | 9 | × | 500 | + | 9 | × | 360 |
| 7524 | − | 360 | A | − | 4180 | + | 200 | A | = | 140 | A | − | 4500 | + | 3240 |
| 3344 | − | 160 | A | = | 140 | A | − | 1260 |
| - | 160 | A | − | 140 | A | = | - | 1260 | − | 3344 |
| - | 300 | A | = | - | 1260 | − | 3344 |
| - | 300 | A | = | - | 4604 |
| 4604 | = | 300 | A |
| 300 | A | = | 4604 |
| A | = | 4604 | ÷ | 300 |
| = | 4604 | × | 1 300 |
| = | 1151 | × | 1 75 |
| A | = | 1151 75 |
| A | = | 15.346667 |