Solve the System by the Substitution Method $$\begin{array} { l } x + y = 12 \\y = x ^ { 2 } - 12 x + 36\end{array}$$

Multiple Choice

Solve the system by the substitution method.
- $$\begin{array} { l } x + y = 12 \\y = x ^ { 2 } - 12 x + 36\end{array}$$

A) $\{ ( 6,6 ) \}$
B) $\{ ( 3,15 ) , ( 8,4 ) \}$
C) $\{ ( - 3,15 ) , ( - 8,20 ) \}$
D) $\{ ( 3,9 ) , ( 8,4 ) \}$