| ( | 20977 5 | + | 37 2 | y | ) | ÷ | ( | 100 | + | y | ) | = | 21 |
| Multiply both sides of the equation by: | ( | 100 | + | y | ) |
| ( | 20977 5 | + | 37 2 | y | ) | = | 21 | ( | 100 | + | y | ) |
20977 5 | + | 37 2 | y | = | 21 | ( | 100 | + | y | ) |
20977 5 | + | 37 2 | y | = | 21 | × | 100 | + | 21 | y |
20977 5 | + | 37 2 | y | = | 2100 | + | 21 | y |
37 2 | y | − | 21 | y | = | 2100 | − | 20977 5 |
| - | 5 2 | y | = | 2100 | − | 20977 5 |
| - | 5 2 | y | = | - | 10477 5 |
10477 5 | = | 5 2 | y |
5 2 | y | = | 10477 5 |
| y | = | 10477 5 | ÷ | 5 2 |
| = | 10477 5 | × | 2 5 |
| y | = | 20954 25 |
| y | = | 838.16 |