Answer: 7 days
Frog: 10 insects a day
Lizard: 14 insects a day
Explanation: The lizard eats 14 incests a day. After 5 days he has eaten 70 insects. I know this because 14x5=70. If the frog wants to eat the same amount, he will need to eat for 7 days to have eaten the same amount of food the lizard has on day 5. I know this because 10x7=70