丽娜共有 1284 根红色和黄色的橡皮筋。她的红色橡皮筋比黄色橡皮筋少 828 根。她将所有红色橡皮筋平均装入红色纸袋中，并将所有黄色橡皮筋装入黄色纸袋中。黄色纸袋的数量是红色纸袋的四倍。每个黄色纸袋装的橡皮筋比每个红色纸袋多 6 根。

1. Find the number of yellow rubber bands using the sum and difference method

Let $Y$ be the number of yellow rubber bands and $R$ be the number of red rubber bands.
We know:
$Y + R = 1284$
$Y - R = 828$
Adding the two equations gives:
$2Y = 1284 + 828 = 2112$
$Y = 2112 \div 2 = 1056$