Michael has 16 CDs. This is four more than twice the amount that Kathleen has. How many CDs does Kathleen have?
Let x = the number of CDs Kathleen has. Four more than twice the number can be written as 2x + 4. Set this amount equal to 16, which is the number of CDs Michael has. To solve this, subtract 4 from both sides of the equation: 2x + 4 - 4 = 16 - 4. Divide each side of the equation by 2: 2x/2 = 12/2. The variable is now alone: x = 6.