Use Cramer's Rule to Solve the System of Equations $x - 3 y = 21$

Multiple Choice

Use Cramer's rule to solve the system of equations. If D = 0, use another method to determine the solution set.
- $x - 3 y = 21$
$- 3 x - 4 y = 15$

A) $\{ ( 2 , - 5 ) \}$
B) Cramer's rule does not apply since $D = 0 ; \varnothing$
C) $\{ ( 3 , - 6 ) \}$
D) $\{ ( - 3 , - 5 ) \}$