What the question means by substitution is that you will take each answer and put it into the original equation. Lets start with a.
a. (6,12): the first number will always be x, so anywhere you see an x in the original equation, put a 6. The second number will always be y, so anywhere you see a y put a 12.
y=x+6y=2x
(12)=(6)+6(12)=2(6)
Does this make sense? Not quite.
b. (-12,-6)
(-6)=(-12)+6(-6)=2(-12)
Does this make sense? No
c. (-6,-12)
(-12)=(-6)+6(-12)=2(-6)
Does this make sense? No
d. (2,4)
(4)=(2)+6(4)=2(2)
Does this make sense? Not just quite.
It seems like it is either A or D but the math says that it is not either of them.
