Translate the Sentence into an Equation, Then Solve $x$ Decreased by 7

Translate the sentence into an equation, then solve.
-A number $x$ decreased by 7.68 is 12.9 .

A) $x-7.68=12.9, x=5.22$
B) $x-7.68=12.9, x=20.58$
C) $7.68-x=12.9, x=5.22$
D) $7.68-x=12.9, x=20.58$