Greg has 7 times as many bookmarks as Sean. If Greg gives 15 bookmarks to Sean, the two children will have exactly the same amount. How many bookmarks do they have altogether?
Sean has S bookmarks
Greg has 7S
So when Greg gives Sean 15 we have that
7S - 15 = S + 15
7S - S = 15 + 15
6S = 30
S = 30 / 6 = 5
7S = 35
Together they have 5 + 35 = 40 bookmarks
