Question

River C is 100 miles longer than River D. If the sum of their lengths is 5,560 miles, what is the length of each river?

Answer 1

$x-\ length\ of\ river\ D\\\\ x+100-\ length\ of\ river\ C\\\\ x+x+100=5560\\\\ 2x+100=5560\ \ \ | subtract\ 100\\\\ 2x=5460\ \ \ | divide\ by\ 2\\\\ x=2730miles\\\\ 2730+100=2830miles\\\\ River\ C\ is\ 2830\ miles\ long\ and \ river\ D\ is\ 2730\ miles\ long.$