The number we need to find is 8.
Work Step by Step
Let X be the number that we need to find. One subtracted from nine times a certain number means 9X - 1. 15 added to seven times the number means 7X + 15. Since both of these expressions are the same, we solve the following equation: 9X - 1 = 7X + 15 2X - 1 = 15 2X = 16 Divide both sides by 2. X = 8 The number is 8.