Maria had some red marbles and some green marbles in a jar. 1/6 of the marbles are red and the rest are green. After she had placed another 60 marbles into the jar, half of the marbles in the jar were green. How many green marbles are there in the jar??

Answer 1

what do we know?
g = 5r
If x of the 60 new marbles are green, then
g+x = r+60-x
so,
5r+x = r+60-x
4r = 60-2x
2r = 30-x
As you can see, there is no unique solution.
(old r, old g) + (x,60-x) → (new r, new g)
If x=0, (15,75)+(60,0)→(75,75)
if x=2, (14,70)+(58,2)→(72,72)
If x=4, (13,65)+(56,4) → (69,69)
and so on, right up to
If x=15, (0,0)+(30,30)→(30,30)