The first one is the answer. Hope i helped you, have a blessed day :)
You divide by 15 y to get x=g/15y
Y=3X+68.25
80=3X+68.25
Subtract 68.25 from both sides
11.75=3X
Divide
11.75/3=3.91
He can't buy a portion of a juice but he doesn't have enough to buy 4
So he can afford 3 juice cartons