Simplify (frac{1}{5x + 5}) + (frac{1}{7x+ 7})

A.
(frac{12}{35x + 1}) 
B.
(frac{1}{35(x + 1)}) 
C.
(frac{12x}{35(x + 7)}) 
D.
(frac{12}{35x + 35})
Correct Answer: Option D
Explanation
(frac{1}{5x + 5}) + (frac{1}{7x+ 7}) = (frac{1}{5(x + 1)}) + (frac{1}{7(x + 1)})
= (frac{7 + 5}{35(x + 1)})
= (frac{12}{35(x + 1)})