164.38 = (1 x 100) + (6 x 10) + (4 x 1) + (3/10) + (8/100)
63/80 x 100 = 78.8%
You divide normally but multiply by 100 (moving the decimal over two places).
The second Version of the game is greater for hitting the down button because substituting any number for x, the second equation would always end up having a greater amount.