Answer:
The answer to your question is: 30 days
Explanation:
City A has 64 unhealthy air quality days this is 4 more than twice the number of unhealthy air quality days in City B.
# unhealthy days in city A = 64
# unhealthy days in city B = B
Equation
64 = 2B + 4
64 -4 = 2B
60 = 2B
B = 30 days