8 divided by 2 is 4.

Take number 8 and cut it into two equal parts with a vertical cut. The right side is 3, and the left is the mirror image of it.

13 and 30... use Chinese characters for numbers. The Chinese logic: 13 is ten, then three... both quite symmetrical. Read it ten plus three. 30 is three, then ten... read it three tens, three times ten.