C is the answer because the second of the 3 numbers is 7 more than 2 times a number. So you would have:
x + (2x + 7 )
Then it says that the third number is 12 less than it so you would have:
x + (2x + 7 ) + (x - 12)
The choice C is the only one that looks the same as the equation I made above.
Hope this helps! Good luck!
