GMAT Quantitative Reasoning Practice Test 1

Write an equation for the question by translating the first sentence. The product of $\mathit{a}$ and $\mathit{b}$ is $\mathit{a}\mathit{b}$, and 11 more than twice the sum of $\mathit{a}$ and $\mathit{b}$ translates to $2\left(\mathit{a}+\mathit{b}\right)+11$. The equation is $\mathit{a}\mathit{b}=2\left(\mathit{a}+\mathit{b}\right)+11$. Substitute 7 for $\mathit{b}.7\mathit{a}=2\left(\mathit{a}+7\right)+11$. This simplifies to $7\mathit{a}=2\mathit{a}+14+11$ by the distributive property and then becomes $7\mathit{a}=2\mathit{a}+25$. Subtract $2\mathit{a}$ from both sides of the equation and then divide each side by $57\mathit{a}-2\mathit{a}=2\mathit{a}-2\mathit{a}+25$.
$\frac{5\mathit{a}}{5}=\frac{25}{5}$
$\mathit{a}=5$. The value of $\mathit{b}-\mathit{a}=7-5=2$.