The equation $x+2y=1$is a ______ equation.

• A linear equation is an equation between two variables that gives a straight line when plotted on a graph.
• A linear equation in two variables is represented in the standard form $ax+by+c=0$. 
• The graph of linear equations with two variables is always a straight line because the two variables each have their unique solutions and point on the graph. 
• The given equation $x+2y=1$ can be in the standard form of $ax+by+c=0$ as $x+2y -1=0$

Therefore, the given equation is a linear equation.