如图，已知点E，F分别在BA，CD的延长线上，连接EF，交AC，BD于G，H点，且∠1=∠2，∠B=∠C．
16．
如图，C岛在A岛的北偏东50°方向，C岛在B岛的北偏西40°方向，则从C岛看A，B两岛的视角∠ACB等于（ ）
如图，C岛在A岛的北偏东50°方向，C岛在B岛的北偏西40°方向，则从C岛看A，B两岛的视角∠ACB等于（ ）| A． | 90° | B． | 80° | C． | 70° | D． | 60° |
12．若方程组$\left\{\begin{array}{l}{2a-3b=13}\\{3a+5b=30}\end{array}\right.$的解是$\left\{\begin{array}{l}{a=8.3}\\{b=1.2}\end{array}\right.$，则方程组$\left\{\begin{array}{l}{2（x+2）-3（y-1）=13}\\{3（x+2）+5（y-1）=30}\end{array}\right.$的解是（ ）
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| A． | $\left\{\begin{array}{l}{x=8.3}\\{y=1.2}\end{array}\right.$ | B． | $\left\{\begin{array}{l}{x=10.3}\\{y=1.2}\end{array}\right.$ | C． | $\left\{\begin{array}{l}{x=6.3}\\{y=2.2}\end{array}\right.$ | D． | $\left\{\begin{array}{l}{x=10.3}\\{y=0.2}\end{array}\right.$ |