Answer:
D. 5/6
Step-by-step explanation:
There are 30 marbles
If you add the black, red, and green marbles together, you get 25
25/30 is equivalent to 5/6
-5x-16=8
-5x=24



above is how to correctly solve the equation
The error is in step 3.
Step 3 as written: 
This is incorrect because you are removing the 5 from the -5x so it wouldn't be in the numerator.
Hope this helps
Answer:
80%
Step-by-step explanation:
8 out of 10 boxes are shaded and when you put it out of 100 you get 80 out of 100. or 80%