7 10 | z | − | 3 10 | × | 2 | ( | z | − | 150 | ) | = | 0 |
| Left side of the equation = | 7 10 | z | − | 3 5 | ( | z | − | 150 | ) |
7 10 | z | − | 3 5 | ( | z | − | 150 | ) | = | 0 |
| Left side of the equation = | 7 10 | z | − | 3 5 | z | + | 3 5 | × | 150 |
| = | 7 10 | z | − | 3 5 | z | + | 90 |
| = | 1 10 | z | + | 90 |
1 10 | z | + | 90 | = | 0 |
1 10 | z | = | 0 | − | 90 |
1 10 | z | = | - | 90 |
| z | = | - | 90 | ÷ | 1 10 |
| = | - | 90 | × | 10 |
| z | = | - | 900 |