Answer:
30 gallons
Step-by-step explanation:
Let c represent the capacity of the container in gallons.
2/5c +8 = 2/3c . . . . adding 8 gallons to 2/5 full gives 2/3 full
8 = (2/3-2/5)c = 4/15c . . . . subtract 2/5c
8(15/4) = c = 30 . . . . . . . . . multiply by 15/4
The container can hold 30 gallons.