To find the greatest decimal, compare place values left to right: ones, tenths, hundredths, thousandths.

Numbers	=	2.083, 2.803, 2.830, 2.038
All have ones digit 2. Compare tenths: 0, 8, 8, 0. 8 is greater. Between 2.803 and 2.830, compare hundredths: 0 < 3. So 2.83 is the greatest.
Greatest	=	2.83