The town used to emit 800 pounds of carbon a year because 80 x 10 = <<80*10=800>>800
20 now take the bus because 80 x .25 = <<80*.25=20>>20
60 people still drive because 80 - 20 = <<80-20=60>>60
Those 60 people create 600 pounds of carbon because 60 x 10 = <<60*10=600>>600
The town now emits 700 pounds of carbon because 100 + 600 = <<100+600=700>>700
The town emits 100 fewer pounds of carbon now because 800 - 700 = <<800-700=100>>100
#### 100