To solve this equation, we need to first combine like terms on the left side:

345 + 12 + 25x = 7, 9, 12

Then simplify:

357 + 25x = 7, 9, 12

Subtract 357 from both sides:

25x = 7, 9, 12 - 357

25x = -348

Now divide by 25 to solve for x:

x = -13.92

Therefore, the solution to the equation is x = -13.92.