503 2/3 = 503.667 (to three decimal places)
Therefore 503 2/3 < 503.7.
Hint: converting to decimal places allows an easy comparison.
Alternatively, we can compare using fractions.
503.7= 503 7/10 = 503 21/30
503 2/3 = 503 20/30
Since 21/30 > 20/30, we conclude that
503.7 = 503 21/30 > 503 20/30 = 503 2/3