The concentration of solution would be the amount of the molecule divided by the volume. In this case, the solution concentration is 36% and the volume is 4 quarts + 1 quarts= 5 quarts. You are asked the concentration before 1 quarts added. The alcohol content should be same for both solutions. The answer should be:
concentration = alcohol content/ volume
alcohol content =concentration * volume
alcohol content1 =alcohol content2
36% * 5 quarts = concentration2 * 4quarts
concentration2= 36% * 5 quarts / 4 quarts= 45%
