Hi!
In order to solve this equation you can either add 31 or 7 to both sides. Since you mentioned 7, we'll go with that. 2x - 7 + 7 = 14x - 31 + 7. Then simplify. 2x = 14x - 24. Then subtract 14x from both sides. -12x = -24. Divide both sides by -12 to get x = 2. Check your answer. 2 * 2 - 7 = 14 * 2 - 31. -3 = -3. So x = 2.