$-2$

2

$-\frac{1}{2}$

$\frac{1}{2}$

$27.5\times {10}^7$

$0.275\times {10}^9$

$2.75\times {10}^8$

$2.75\times {10}^9$

$x⩾-2$

$x⩽-2$

$x⩾2$

$x⩽2$

$\left\{\begin{array}{c}9x+11=y\\ 6x+16=y\end{array}\right.$

$\left\{\begin{array}{c}9x-11=y\\ 6x-16=y\end{array}\right.$

$\left\{\begin{array}{c}9x+11=y\\ 6x-16=y\end{array}\right.$

$\left\{\begin{array}{c}9x-11=y\\ 6x+16=y\end{array}\right.$