To determine which equation is true, let's replace "x" with "12" in each equation and solve.
Let's start with Option A.
For Option A, at x = 12, the value is not equal to 51 hence, Equation A is not true.
For Option B:
As we can see, Option B is not also true.
Let's check Option C.
Option C is also not true.
Let's check Option D.
As we can see, at x = 12, Equation D is equal to 39. Hence, Equation D is true.