To sum it up for you, a pair of AirPods is equal 10, a person is equal 5, and a pair of smartwatches equals 4. So the last expression should be one AirPod which is 5, a person is another 5, and a single smartwatch is 2. So the total is 5 by 2 plus 5, which is 15.
總結一下,一對 AirPods 等於 10,一個人等於 5,一對智能手錶等於 4。是以,最後的表達式應該是一個 AirPod 等於 5,一個人等於 5,一塊智能手錶等於 2。