Let the magazine be m and the eraser be e. Then the total cost is 25.
The equation can now be shown as follows;
[tex]\begin{gathered} 25=m+4e \\ 25=5+4e \\ Subtract\text{ 5 from both sides of the equation;} \\ 20=4e \\ \text{Divide both sides of the equation by 4} \\ 5=e \end{gathered}[/tex]Therefore each eraser cost $5