Use the Method of Substitution to Find the X -Coordinate $a + b i$

Multiple Choice

Use the method of substitution to find the x -coordinate of the solution of the following system of equations. $a + b i$

A) $( 5 - 2 i ) ( 2 + 5 i )$
B) $12 + 5 i$
C) $16 + 21 i$
D) $14 - 2 i$