| 4 | ( | 5 | a | × | 2 | + | 10 | a | + | 21 | ) | × | 2 | = | 45 | ( | 20 | a | × | 2 | + | 72 | a | + | 68 | ) |
| Left side of the equation = | 8 | ( | 5 | a | × | 2 | + | 10 | a | + | 21 | ) |
| 8 | ( | 5 | a | × | 2 | + | 10 | a | + | 21 | ) | = | 45 | ( | 20 | a | × | 2 | + | 72 | a | + | 68 | ) |
| Left side of the equation = | 8 | × | 5 | a | × | 2 | + | 8 | × | 10 | a | + | 8 | × | 21 |
| = | 80 | a | + | 80 | a | + | 168 |
| = | 160 | a | + | 168 |
| 160 | a | + | 168 | = | 45 | ( | 20 | a | × | 2 | + | 72 | a | + | 68 | ) |
| Right side of the equation = | 45 | × | 20 | a | × | 2 | + | 45 | × | 72 | a | + | 45 | × | 68 |
| = | 1800 | a | + | 3240 | a | + | 3060 |
| = | 5040 | a | + | 3060 |
| 160 | a | + | 168 | = | 5040 | a | + | 3060 |
| 160 | a | − | 5040 | a | = | 3060 | − | 168 |
| - | 4880 | a | = | 3060 | − | 168 |
| - | 4880 | a | = | 2892 |
| - | 2892 | = | 4880 | a |
| 4880 | a | = | - | 2892 |
| a | = | - | 2892 | ÷ | 4880 |
| = | - | 2892 | × | 1 4880 |
| = | - | 723 | × | 1 1220 |
| a | = | - | 723 1220 |
| a | = | - 0.592623 |