совете дроби 5/72 и 7/90

Приводим к общему знаменателю.

5/(8*9) и 7/(9*10); (5*10)/(8*9*10) и (7*8)/(8*9*10); 50/720 и 56/720

50/720 < 56/720 -> 5/72 < 7/90