| 7980000 | = | 100 | ( | 20000 | − | 600 | m | ) | + | 80 | ( | 30000 | − | 400 | m | ) | + | ( | 160 | − | m | ) | ( | 20000 | + | 1000 | m | ) |
| Right side of the equation = | 100 | × | 20000 | − | 100 | × | 600 | m | + | 80 | ( | 30000 | − | 400 | m | ) | + | ( | 160 | − | m | ) | ( | 20000 | + | 1000 | m | ) |
| = | 2000000 | − | 60000 | m | + | 80 | ( | 30000 | − | 400 | m | ) | + | ( | 160 | − | m | ) | ( | 20000 | + | 1000 | m | ) |
| = | 2000000 | − | 60000 | m | + | 80 | × | 30000 | − | 80 | × | 400 | m | + | ( | 160 | − | m | ) | ( | 20000 | + | 1000 | m | ) |
| = | 2000000 | − | 60000 | m | + | 2400000 | − | 32000 | m | + | ( | 160 | − | m | ) | ( | 20000 | + | 1000 | m | ) |
| = | 4400000 | − | 92000 | m | + | ( | 160 | − | m | ) | ( | 20000 | + | 1000 | m | ) |
| = | 4400000 | − | 92000 | m | + | 160 | ( | 20000 | + | 1000 | m | ) | − | m | ( | 20000 | + | 1000 | m | ) |
| = | 4400000 | − | 92000 | m | + | 160 | × | 20000 | + | 160 | × | 1000 | m | − | m | ( | 20000 | + | 1000 | m | ) |
| = | 4400000 | − | 92000 | m | + | 3200000 | + | 160000 | m | − | m | ( | 20000 | + | 1000 | m | ) |
| = | 7600000 | + | 68000 | m | − | m | ( | 20000 | + | 1000 | m | ) |
| = | 7600000 | + | 68000 | m | − | m | × | 20000 | − | m | × | 1000 | m |
| = | 7600000 | + | 48000 | m | − | m | × | 1000 | m |
| 7980000 | = | 7600000 | + | 48000 | m | − | m | × | 1000 | m |