Answer:
August 12 is the next practice
Explanation:
So, the problem says that Nick has tennis practice every sixth day, and Mark has is every fourth day.
To find this you have to know the LCM of 6 and 4 which is 12
6: 6,12,18,24,30,36,42,48,54,60
4: 4,8,12,16,20,24,28,32,36,40
LCM of 6 and 4 = 12
Now as we know that the LCM of 6 and 4 is 12 we add on to July 31st so we get August 12.