Question

Can anyone explain this?

Answer 1

See this and follow the same any where you see a fraction like that...
1 - (a/b) = (b-a) / b

;)
Hope it helps

Answer 2

$= \frac{1 - \frac{64}{113} }{1 - \frac{49}{113} } \\ = \frac{ \frac{113 - 64}{113} }{ \frac{113 - 49}{113} } \\ = \frac{ \frac{49}{113} }{ \frac{64}{113} } \\ = \frac{49}{113} \times \frac{113}{64} \\ = \frac{49}{64} \\ \\ or \\ \\ 0.765$