A long distance phone call is made using 10-10-220. They
charge $0.99 for the first 20 minutes, and $0.07 for each
additional minute. A long distance phone call, using 10-10-220,
costs a total of $2.81. Find the total number of minutes used to
make this long distance phone call. Let a represent the number
of additional minutes used. This is a two step word problem