Solve the System by the Substitution Method $$\begin{array} { l } y = 7 x ^ { 2 } - 14 x \\y = 7 x\end{array}$$

Multiple Choice

Solve the system by the substitution method. $$\begin{array} { l } y = 7 x ^ { 2 } - 14 x \\y = 7 x\end{array}$$

A) $\{ ( 0,0 ) , ( 3,21 ) \}$
B) $\{ ( 3,21 ) \}$
C) $\{ ( 0,0 ) \}$
D) { }