Cassandra measured her height as 63 inches. That is 6 inches less than 3 times her younger brother’s height. How tall is her younger brother?
Let's call Cassandra's younger brother's height x inches.
According to the information given, 63 inches is 6 inches less than 3 times her younger brother's height.
So, we can set up the equation 3x - 6 = 63.
Adding 6 to both sides, we have 3x = 69.
Dividing both sides by 3, we find that x = 23.
Therefore, Cassandra's younger brother's height is 23 inches.