Answer
$y=\frac{x}{2}.$
Work Step by Step
If two lines are parallel then their slopes must be equal.
We know that if the slope of a line is $m$ and it contains $P_1(x_1,y_1)$, then its equation is: $y-y_1=m(x-x_1).$ It is parallel to $x-2y=-5$, which is $y=\frac{x}{2}+\frac{5}{2}$, then its slope is $m=\frac{1}{2}$. Hence here: $y-0=\frac{1}{2}(x-0)\\y=\frac{x}{2}.$
