Which linear system has the solution (6, 6)

a: 4x - 3y = -1 -2x + y = -3
b: x + y = 12 3x - 2y = 6
c: 3x + y = 4 4x - 3y = 1
d: 4x + 3y = 0 2x - y = 0

This question awards 100 ! i really don’t want to fail i will also mark you !

Given the expression (7 ? 4i) ? (2 + 6i), perform the indicated operation and write the answer in the form a + bi.

Statements reasons 1. ab ? cd; ad ? bc 1. given 2. ac ? ac 2. reflexive property 3. ? adc ? ? cba 3. ? 4. ? dac ? ? bca; ? acd ? ? cab 4. cpctc 5. ? dac and ? bca are alt. int. ? s; ? acd and ? cab are alt. int. ? s 5. definition of alternate interior angles 6. ab ? cd; ad ? bc 6. converse of the alternate interior angles theorem 7. abcd is a parallelogram 7. definition of parallelogram what is the missing reason in step 3?