Take out the 1 red ball for the first time and don't put it back. There are six balls left.

The probability of taking out the white ball is 3/6= 1/2.

This question is a bit vague. For example, "Take out 1 red ball for the first time, don't put it back" is a condition, then the probability of taking out the white ball for the second time should be1/2; If "taking out 1 red ball for the first time and not putting it back" is not a condition but a process, then the probability of taking out the white ball for the second time should be 4/7× 1/2=2/7.