We have been given a table of overnight low temperature for a four-day period. We are supposed to give a possible temperature for Wednesday.
We are told that the low temperature on Wednesday was between the second and third highest temperature.
Let us place our given temperatures from least to greatest order.
Sunday (-11), Thursday (-8), Friday (7), Sunday (18)
We can see that second and third highest temperatures are -8 and 7 respectively.
Any number between -8 and 7 will be a possible temperature for Wednesday. 3 can be a possible temperature for Wednesday as 3 is between -8 and 7.