| ( | 300 | − | 40 | ) | a | + | 40 | × | 7 10 | a | = | 9 5 | ( | 4000 | + | 8800 | ) |
| Left side of the equation = | ( | 300 | − | 40 | ) | a | + | 28 | a |
| ( | 300 | − | 40 | ) | a | + | 28 | a | = | 9 5 | ( | 4000 | + | 8800 | ) |
| Left side of the equation = | 300 | a | − | 40 | a | + | 28 | a |
| = | 288 | a |
| 288 | a | = | 9 5 | ( | 4000 | + | 8800 | ) |
| Right side of the equation = | 9 5 | × | 4000 | + | 9 5 | × | 8800 |
| = | 7200 | + | 15840 |
| = | 23040 |
| 288 | a | = | 23040 |
| a | = | 23040 | ÷ | 288 |
| = | 23040 | × | 1 288 |
| = | 80 | × | 1 |
| a | = | 80 |