GMAT Quantitative Reasoning Practice Test 1

Let $\mathit{x}=$ Sam's current age and $3\mathit{x}=$ John's current age. If John will be twice as old as Sam in six years, this sets up the equation $3\mathit{x}+6=2\left(\mathit{x}+6\right)$.Solve this equation for $\mathit{x}$ by using the distributive property on the right side of the equation and then subtracting $2\mathit{x}$ from both sides. $3\mathit{x}+6=2\mathit{x}+12.3\mathit{x}-2\mathit{x}+6=2\mathit{x}-2\mathit{x}+12$ Subtract 6 from both sides. $\mathit{x}+6-6=12-6.\mathit{x}=6$. Since $\mathit{x}$ is Sam's current age, Sam was four years old two years ago.