Answer:
Highlighter of 11 grams is greater mass. 
Step-by-step explanation:
One highlighter has a mass of 11 grams. 
Another highlighter has a mass of 10,800 milligrams.
We need to find which one greater mass. 
We can see both unit of mass different. 
First we have to make it same unit and then we compare it. 
Highlighter 1 = 11 grams 
Highlighter 2 = 10,800 milligrams 
We will change milligram to gram .
As we know 1000 milligram = 1 gram 
In 1000 milligrams = 1 gram 
       1 milligram       = 0.001 gram 
In 10,800 milligrams = 0.001 x 10800 = 10.8 grams 
Now we will compare 11 and 10.8 number because both are in same unit. 
11 > 10.8 
Highlighter 1 > Highlighter 2
Hence, Highlighter of 11 grams is greater mass.