Solve the System by the Substitution Method $$x ^ { 2 } + y ^ { 2 } = 49$$

Multiple Choice

Solve the system by the substitution method.
- $$x ^ { 2 } + y ^ { 2 } = 49$$
$y - x = 7$

A) $\{ ( 0,7 ) , ( 7,0 ) \}$
B) $\{ ( 0 , - 7 ) , ( - 7,0 ) \}$
C) $\{ ( 0,7 ) , ( - 7,0 ) \}$
D) $\{ ( 0 , - 7 ) , ( 7,0 ) \}$