Answer: There were 5 volunteers in each original group.
Explanation:
Hi to answer this question we have to write equations with the information given: 
"Litter cleanup volunteers form 4 groups containing v volunteers each "
x/4 =v (first equation)
Where: 
- x = initial number of volunteers 
- v = number of volunteers in each original group 
"Then 10 more volunteers show up the volunteers regroup into 5 groups each containing 6 people." So we have to add 10 to the original number of volunteers (x) and divide it by 5 , to obtain 5 groups . That expression equals 6. 
Mathematically speaking :
(x+10 )/5 = 6 (second equation)
Solving for x 
x/5 +2 =6 
x/5= 6-2 
x/5= 4 
x =4(5) 
x = 20 
Replacing x in the first equation 
20/4 =v =5 
There were 5 volunteers in each original group.