With sed's -e option you can string together multiple sed action's.
echo -e "Monday\nTuesday" | sed -e 's/Mon/Sun/' -e '/Tuesday/d'
The above changes Mon to Sun (blue part) and also looks for lines that contain Tuesday and deletes them (green part). You cannot do this in one action, two are needed. You need the -e option for this (or use 2 seperate sed statements, which is not always possible).
There is one thing that you need to be aware of; Changes made in the first action are noticed in the second (third, ... ) action. Have a look at this simple silly example:
echo "sunday" | sed -e 's/sunday/night/' -e 's/night/week/'
The first action looks for sunday and changes this into night, the second action looks for night and changes this into week.
Have a look at this link as well: Sed - An Introduction and Tutorial