Answer: 1/5
Step-by-step explanation: Since the probability of picking an orange is 1/3, you'll need to multiply 5 by 3 to find the total number of parts. This will give you 15. So since you know that there are 15 parts in total, you'll need to do the calculation 15-(5+7) to give you the ratio of lemons, which is 3. To find the probability, you simply just have to put the ratio of lemons over the total number of parts, giving you 3/15. Now, all you need to do is simplify. As 3 goes into 15 5 times, the simplified fraction is 1/5.