I start with $9-2x$ widgets. Each day, I produce $2x+1$ widgets, and destroy $3-x$ widgets. After three days, how many widgets am I left wit

start     9-2x

end of day one  add         +2x+1   - (3-x)

end of day two  add         +2x+1   - (3-x)

end of day two  add         +2x+1   - (3-x)

 

Add them up!