GMAT Quantitative Reasoning Practice Test 7

Plug in numbers. The first statement will work when $\mathit{a}=3$ and $\mathit{b}=2$, for example and then ${\mathit{a}}^2=9$ and ${\mathit{b}}^2=4$. However, it will not work when $\mathit{a}=\left(-2\right)$ and $\mathit{b}=\left(-3\right)$, then ${\mathit{a}}^2=4$, and ${\mathit{b}}^2=9$. The second statement is sufficient, it is possible to subtract $\mathit{d}$ from both sides of the inequality and get: $\mathit{a}+\mathit{d}-\mathit{d}>\mathit{b}+\mathit{d}-\mathit{d}$, or $\mathit{a}>\mathit{b}$.