| 13 | ÷ | 20 | + | ( | 16 | − | a | ) | ÷ | 30 | = | 1 |
| Left side of the equation = | 13 20 | + | ( | 16 | − | a | ) | × | 1 30 |
13 20 | + | ( | 16 | − | a | ) | × | 1 30 | = | 1 |
| Left side of the equation = | 13 20 | + | 16 | × | 1 30 | − | a | × | 1 30 |
| = | 13 20 | + | 8 15 | − | a | × | 1 30 |
| = | 71 60 | − | 1 30 | a |
71 60 | − | 1 30 | a | = | 1 |
| - | 1 30 | a | = | 1 | − | 71 60 |
| - | 1 30 | a | = | - | 11 60 |
11 60 | = | 1 30 | a |
1 30 | a | = | 11 60 |
| a | = | 11 60 | ÷ | 1 30 |
| = | 11 60 | × | 30 |
| = | 11 2 | × | 1 |
| a | = | 11 2 |
| a | = | 5.5 |