Leah has 28 more marbles than Dan. 1/3 of the marbles Leah has is equal to 4/5 of the marbles Dan has. Find the number of marbles Leah has.
Dan's marbles --- x
Leah's marbles --- x + 28
(1/3)(x+28) = (4/5)x
times 15
5(x+28) = 12x
5x + 140 = 12x
Take it from here
If Leah has x marbles, then
1/3 x = 4/5 (x-28)
Now finish it off