Answer
The system has an infinite number of solutions.
Solution set = $\{(x,y)\ |\ y=2x\}$
Work Step by Step
Graph each line
(plot two points per line, such as the intercepts)
$2x-y=0:\quad \left[\begin{array}{lll}
x=0 & ... & x=1\\
0-y=0 & & 2-y=0 \\
y=0 & & y=2\\
(0,0) & & (1,2)
\end{array}\right]$
$y=2x:\quad \left[\begin{array}{lll}
x=0 & ... & x=1\\
y=0 & & y=2\\
& & \\
(0,0) & & (1,2)
\end{array}\right]$
The lines coincide.
The system has an infinite number of solutions.
Solution set = $\{(x,y)\ |\ y=2x\}$
