Basic Algebra/Systems of Linear Equations/Chapter Test

Please post your test problems this way:

• Problem:(answer,level of difficulty(easy, medium, hard))
• Example

　$x+11=36$:

($x=36-11=25$,  easy)

$\{\begin{array}{c}x+11=y+111\\ y=-3x\end{array}$

$x+11=-3x+111$

$x=25$ ,($25+11=36$)

($y=36-111=-75$, medium)