The ratio of Morgan's bookmarks to Tracy's bookmarks was 4 to 3. Morgan gave half of her bookmarks to Tracy. She counted her remaining bookmarks and found that she now had 9 fewer bookmarks than Tracy. How many bookmarks did Morgan have at first?
Morgan starts with 4k bookmarks and Tracey starts with 3k bookmarks
Morgen give half of hers to Tracey so now Morgan has 2k bookmarks and Tracey has 5k bookmarks
BUT morgen has 9 more than Tracey which means that Mogen must have 5k-9 bookmarks
So Tracy has 2k bookmarks which is also 5k-9 bookmarks
which means that
2k=5k-9
Once you find k substitute it back to fin how many bookmarks Morgan started with.