Let x and y be integers. Show that 9x + 5y is divisible by 19 if and only if x + 9y is divisible by 19.
+591 if 9x + 5y is divisible by 19 only if x + 9y is divisible by 19, that means that if we subtract them from each other, it should be divisible by 19. to make this simpler, we can multiple x + 9y by 9, so we can remove the x. once we subtract, we get 76, which is divisible by 19. So this means that when one is divisble by 19, the other is as well.
