Switch statements don't work the same as if statements, you cant test for a range of number. You can only check for specific numbers. In your case, you should just use if statements.
if guess is greater then num output to high
else if guess is less then num output low
else output you guessed the number
Note switch statements can be used to test other data types then just integers.
Please also use code tags next time, they're the <> on the right side of the submission box.