We are given that

.
Substitute x with 5-x, then the above equation becomes:

, that is

So, we have the following system of equations:
i)

ii)

multiply the first equation by -4, so that we eliminate f(5-x)'s
i)

ii)

adding the 2 equations side by side we have:

expanding the binomial, and collecting same terms we have:


dividing by -5:

dividing by 3:

Answer:
Answer:
C.
Step-by-step explanation:
if wrong then pls contact me in the comment section
4d + 12 = 4(d + 3)
Basically, you just need to determine what 4d and 12 have in common. In this case, they both divide evenly by 4. Therefore 4 (d + 3) = 4d + 12 according to the distributive property.