Let \( x \) represent the height of Cassandra's younger brother in inches. According to the problem, Cassandra's height of 63 inches is 6 inches less than 3 times her brother's height. We can translate this statement into an equation.
The equation can be set up as follows:
\[ 3x - 6 = 63 \]
This equation is now in the form \( px + q = r \), where:
- \( p = 3 \)
- \( q = -6 \)
- \( r = 63 \)
Now, to find the height of her younger brother, we can solve this equation.
First, add 6 to both sides:
\[ 3x = 63 + 6 \] \[ 3x = 69 \]
Next, divide both sides by 3:
\[ x = \frac{69}{3} \] \[ x = 23 \]
Thus, Cassandra's younger brother is 23 inches tall.