Let Lyle's age be represented by \( x \). Since their ages are three consecutive even numbers, Katrina's age would be \( x + 2 \) and Mari's age would be \( x + 4 \).
The equation representing their combined ages would be:
\[ x + (x + 2) + (x + 4) = 66 \]
Simplifying this equation:
\[ x + x + 2 + x + 4 = 66 \] \[ 3x + 6 = 66 \]
This equation can be used to determine the age, \( x \), of Lyle.