Answer:
The answer is 4
Step-by-step explanation: If you multiply $4 by 4(hotdogs) you will get 16 then if you subtract $22(the total) from 16 it will lead to six which is a reasonable price for water.
Next is to test the answer on the next part. $4 x 8(hotdogs) is 32 then subtract 35 from it and it will lead to the same price of water. (Also I tested all the other answers and they didn't match)