A marathon is 26 miles.  He can run the first 10 miles in 1 hour.  For the remaining miles he runs at 80% that pace.  How long does the race take?
There are 26-10=<T>subtract(26, 10)=16 miles left for the rest of the race
He runs 10*.8=<T>multiply(10, 0.8)=8.0 miles per hour
So it takes him 16/8=<T>divide(16, 8)=2.0 hours
So in total it takes 1+2=<T>add(1, 2)=3 hours
