| ( | 160 | + | 80 | × | 7 8 | + | 20 | ( | 2 | + | b | ) | ( | 1 | + | b | ) | ÷ | 2 | ) | = | ( | 1 | + | b | ÷ | 2 | ) | ( | 160 | + | 80 | × | 7 8 | + | 20 | ( | 2 | + | b | ) | ) |
| Left side of the equation = | 160 | + | 80 | × | 7 8 | + | 20 | ( | 2 | + | b | ) | ( | 1 | + | b | ) | ÷ | 2 |
| = | 160 | + | 70 | + | 10 | ( | 2 | + | b | ) | ( | 1 | + | b | ) |
| = | 230 | + | 10 | ( | 2 | + | b | ) | ( | 1 | + | b | ) |
| = | 230 | + | 10 | × | 2 | ( | 1 | + | b | ) | + | 10 | b | ( | 1 | + | b | ) |
| = | 230 | + | 20 | ( | 1 | + | b | ) | + | 10 | b | ( | 1 | + | b | ) |
| = | 230 | + | 20 | × | 1 | + | 20 | b | + | 10 | b | ( | 1 | + | b | ) |
| = | 230 | + | 20 | + | 20 | b | + | 10 | b | ( | 1 | + | b | ) |
| = | 250 | + | 20 | b | + | 10 | b | ( | 1 | + | b | ) |
| = | 250 | + | 20 | b | + | 10 | b | × | 1 | + | 10 | b | b |
| = | 250 | + | 20 | b | + | 10 | b | + | 10 | b | b |
| = | 250 | + | 30 | b | + | 10 | b | b |
| 250 | + | 30 | b | + | 10 | b | b | = | ( | 1 | + | b | ÷ | 2 | ) | ( | 160 | + | 80 | × | 7 8 | + | 20 | ( | 2 | + | b | ) | ) |
| Right side of the equation = | 1 | ( | 160 | + | 80 | × | 7 8 | + | 20 | ( | 2 | + | b | ) | ) | + | b | ÷ | 2 | × | ( | 160 | + | 80 | × | 7 8 | + | 20 | ( | 2 | + | b | ) | ) |
| = | 1 | × | 160 | + | 1 | × | 80 | × | 7 8 | + | 1 | × | 20 | ( | 2 | + | b | ) | + | b | × | 1 2 | ( | 160 | + | 80 | × | 7 8 | + | 20 | ( | 2 | + | b | ) | ) |
| = | 160 | + | 70 | + | 20 | ( | 2 | + | b | ) | + | b | × | 1 2 | ( | 160 | + | 80 | × | 7 8 | + | 20 | ( | 2 | + | b | ) | ) |
| = | 230 | + | 20 | ( | 2 | + | b | ) | + | b | × | 1 2 | ( | 160 | + | 80 | × | 7 8 | + | 20 | ( | 2 | + | b | ) | ) |
| = | 230 | + | 20 | × | 2 | + | 20 | b | + | b | × | 1 2 | ( | 160 | + | 80 | × | 7 8 | + | 20 | ( | 2 | + | b | ) | ) |
| = | 230 | + | 40 | + | 20 | b | + | b | × | 1 2 | ( | 160 | + | 80 | × | 7 8 | + | 20 | ( | 2 | + | b | ) | ) |
| = | 270 | + | 20 | b | + | b | × | 1 2 | ( | 160 | + | 80 | × | 7 8 | + | 20 | ( | 2 | + | b | ) | ) |
| = | 270 | + | 20 | b | + | b | × | 1 2 | × | 160 | + | b | × | 1 2 | × | 80 | × | 7 8 | + | b | × | 1 2 |
| = | 270 | + | 20 | b | + | b | × | 80 | + | b | × | 35 | + | b | × | 10 | ( | 2 | + | b | ) |
| = | 270 | + | 135 | b | + | b | × | 10 | ( | 2 | + | b | ) |
| = | 270 | + | 135 | b | + | b | × | 10 | × | 2 | + | b | × | 10 | b |
| = | 270 | + | 135 | b | + | b | × | 20 | + | b | × | 10 | b |
| = | 270 | + | 155 | b | + | b | × | 10 | b |
| b= | - | 4 25 |