Final answer:
Marcie replaced 2 out of the 5 panes of glass in a window. She replaced 40% of the glass.
Step-by-step explanation:
To find the percentage of glass replaced by Marcie, we need to divide the number of panes she replaced by the total number of panes and then multiply by 100. In this case, Marcie replaced 2 panes out of 5. So, the percentage of glass she replaced is:
(2/5) * 100 = 40%
Therefore, Marcie replaced 40% of the glass.