7.
如图,在?ABCD中,∠D=120°,则∠A的度数等于( )
| A. | 120° | B. | 60° | C. | 40° | D. | 30° |
3.已知$\left\{{\begin{array}{l}x=1\\ y=1\end{array}}\right.$,$\left\{{\begin{array}{l}x=2\\ y=3\end{array}}\right.$是关于x,y的二元一次方程y=kx+b的解,则k,b的值是( )
| A. | k=1,b=0 | B. | k=-1,b=2 | C. | k=2,b=-1 | D. | k=-2,b=1 |
2.已知二元一次方程2x-7y=5,用含x的代数式表示y,正确的是( )
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| A. | $y=\frac{2x+5}{7}$ | B. | $y=\frac{2x-5}{7}$ | C. | $x=\frac{5+7y}{2}$ | D. | $x=\frac{5-7y}{2}$ |