Answer:
3/10 or 30%
Step-by-step explanation:
Add all of the marbles: 5+2+3=10
Then use a fraction to represent the three purple marbles: 3/10
That porportion is your answer
8x + 12 = 3x + 5x + 12
8x + 12 = 8x + 12
Bringing like terms on one side
8x - 8x = 12 - 12
x = 0