| ( | a | − | 50 | ) | ÷ | 20 | = | ( | 70 | − | a | ) | ÷ | 45 |
| Left side of the equation = | a | × | 1 20 | − | 50 | × | 1 20 |
| = | a | × | 1 20 | − | 5 2 |
1 20 | a | − | 5 2 | = | ( | 70 | − | a | ) | ÷ | 45 |
| Right side of the equation = | 70 | × | 1 45 | − | a | × | 1 45 |
| = | 14 9 | − | a | × | 1 45 |
1 20 | a | − | 5 2 | = | 14 9 | − | 1 45 | a |
1 20 | a | + | 1 45 | a | = | 14 9 | + | 5 2 |
13 180 | a | = | 14 9 | + | 5 2 |
13 180 | a | = | 73 18 |
| a | = | 73 18 | ÷ | 13 180 |
| = | 73 18 | × | 180 13 |
| = | 73 | × | 10 13 |
| a | = | 730 13 |
| a | = | 56.153846 |