Total number of ways that each select one shirt without any condition = 4P4 = 4! = 24
Number of ways Arun chooses red or Shweta chooses white
= Number of ways Arun chooses red + Number of ways Shweta chooses white - Number of ways Arun chooses red and Shweta chooses white
= 3P3 + 3P3 - 2P2
= 3! + 3! - 2!
= 10
∴ Required number of ways = 24 - 10 = 14