Answer: hello mate!
Sara feeds her fish every 2 days: this means that if we took the 0 in a day that she feed both animals; then the fish gets food on the day 2, on the day 4, on the day 6, etc
And the snake gets food on days 6, 12, 18, etc.
now we want to count the number of days where both animals get food on the same day. Because 6 is a multiple of 2, we can see that every day that the snake is feed, the fish also feed, this is because the minimal common multiple between 2 and 6 is 6.
then we can see that each 6 days Sarah feeds her fish and snake on the same day. Now we need to see the number of times that this event happens in 30 days; we can see this dividing 30 days by 6 days:
30/6 = 5
Then in the span of 30 days, there are 5 times where both animals get food on the same day.
