18s primemail factors are 2×3×3
Hello! Seeings 20 is less than 50, you then need to round down. If its over 50 then you round up! So if you have 14 its rounded to 10. And if you have 16 round it to 20. So 820 is rounded to 800.
3 1/4 is the right answer
100 (10)
121 (11)
144 (12)
169 (13)
196 (14)
