Since the tenths digit is 5 (or over), you would round 3.5 up to 4.
350
503.8, when rounded to the nearest whole number, is 504.
650
It is 5 rounded to the nearest whole number
12
350
350
345 rounded to the nearest 10 is 350
8
350
350
503.8, when rounded to the nearest whole number, is 504.
350
650
350
30
76